Oh, one more thing. I also tried this here: https://support.mozilla.org/en-US/questions/1091990

But some genius thought it would be a great idea to exclude the feature to start Thunderbird in Safe mode in Thunderbird 5. And as I can't access any menu, I can't restart Thunderbird without the plugins and extensions...

OK. One step forward.

Found the profile folder, went into extensions, looked into the folders with totally cryptic names (why can't we have speaking folders for the extensions???) and I think I found the correct folder of the "Provider for Google Calendar" plugin and deleted it. Now Thunderbird seems to work again for emails. I guess I will only give Provider another try tonight. Lost so much worktime already.

I'm using Thunderbird 56 (beta) and it still has Safe Mode. I can't think why you believe this has been removed.

Now you have removed Provider, you could try to download and install it again. Unless you're running a pre-release beta version, this should get you the current version of the addon.

First of all: Thank you for your reply! Zenos said

I'm using Thunderbird 56 (beta) and it still has Safe Mode. I can't think why you believe this has been removed.

I believe that, because the Mozilla website says so and because I can't start Thunderbird in safe mode with "shift" as described here: https://support.mozilla.org/en-US/kb/safe-mode-thunderbird

Note: In Thunderbird versions prior to 5, there was a shortcut on the Windows start menu for Thunderbird Safe Mode. As of Thunderbird 5 this item has been removed, and replaced with a Restart with Add-ons Disabled entry on the help menu.

I can't use the last option if Thunderbird is completely blocked and wouldn't react to anything, so I would need to start Thunderbird already in safe mode. But starting it with "Shift" isn't working and there is nothing in the start menu.

I am using 52.3.0 (32-bit) at the moment. I'll give the "Provider" another try after work. Receiving and sending emails is more important than the calendar entries at the moment.

You can start it from the command prompt, with a -safe-mode command line switch.

Linux doesn't afford the luxury of a start menu option, so we Linux users have always had to do it this way

For Safe Mode: most likely you hold down Shift only when clicking the shortcut and release it, but you should hold it for a few seconds. This may not be clear, but it’s the small difference between "press" and "hold down". ;)

If you would like to have a shortcut for Safe Mode: you can create a copy of your existing Thunderbird shortcut and add -safe-mode to the Target field in its properties, after the command line option ending with " and separated by a space. ("C:\Program Files\Mozilla Thunderbird\thunderbird.exe" -safe-mode)

For your issue with the calendar, try this:

1. Start Thunderbird in Safe Mode and disable the Provider for Google Calendar add-on in the Add-ons Manager.
2. Close Thunderbird, and restart it in regular mode.
3. Remove (not just disable) the Google calendar from Lightning.
4. Restart Thunderbird and enable the Provider for Google Calendar add-on.
5. Add the removed Google calendar to Lightning.

Apparently you removed the add-on the hard way, so entries for it may be left somewhere (hence this is not advised) but it should resolve itself when reinstalling. The whole trick is to add the calendar after installing the add-on - it may have trouble recognizing the calendar if not.

Source: this bug.

Does any of this help?

Thank you Zenos and Tonnes for the answer.

For Safe Mode: most likely you hold down Shift only when clicking the shortcut and release it, but you should hold it for a few seconds. This may not be clear, but it’s the small difference between "press" and "hold down". ;)

I actually held down the "Shift" button for a while, but obviously not long enough. Tried it again and it worked.

Holch said

I actually held down the "Shift" button for a while, but obviously not long enough. Tried it again and it worked.

Did you get your provider issue sorted out?

Wayne Mery said

Did you get your provider issue sorted out?

My problem was solved to the point that I can use Thunderbird again. The problem with Provider is not solved yet. I didn't have much time to look into this last week, but at least I could work with Thunderbird again (but without the Google Calendars).

Today I tried to install Provider again and it says that provider for Google Calendar is not compatible with my Thunderbird version. I'll have to do some research on this.

Attached a screenshot of how it looks like. I guess I will just have to wait a while until provider is updated?

What is really weird is that my colleague just confirmed that she has the same version and she has Provider for Google Calendar installed... This is really weird. I already uninstalled Lightning (read that in some other post, I think the suggestion was from Zenos), but this did not change anything.

Is Lightning working properly now? If not, you would first need to make sure it is enabled and working. You should not need to install Lightning again from AMO, but just remove any existing add-on, then restart Thunderbird, then Enable Lightning in the Add-ons Manager and restart when prompted. It should show up there as disabled after uninstalling a previous add-on, since it is installed (but disabled) in recent Thunderbird versions by default.

If for some reason you can’t download the most recent Provider add-on (3.3) from within Thunderbird’s Add-ons Manager, you could try downloading it from here in a browser, and then install it manually using the cogwheel in Thunderbird’s Add-ons Manager, or drag it there.

Installing an Add-on in Thunderbird

I installed provider via the manual way, because I could not get it through the search on the add-ons manager.

But it went directly back into all the calenders (without me choosing them) and I am basically back to square one. Same problem as before, Thunderbird is totally blocked due to the error messages.

Problem are probably the many recurring events (monthly events to remind me of certain things like payments that are due, tasks that need to be done by a certain date, etc.).

Probably will need to kill Provider again. I'll keep you updated.

As suggested earlier, did you remove the calendar itself prior to uninstalling/reinstalling/enabling the Provider add-on and then add it again?

Hi Tonnes, thanks for the patiences.

Yes, I deleted the folder of provider first (to unlock Thunderbird again, as I couldn't do anything with it). Then I uninstalled Lightning and installed it again. It is activated.

Unless I understand you wrong, please have another look at the steps and linked bug, taking note at comment 6 and 7. You would need to remove the existing calendar from Lightning first (unsubscribe), restart Thunderbird (the slowness should be gone) and then re-add the calendar. Did you try that?

@Tonnes: And here is the problem. As long as Provider is installed, I can't do anything with Thunderbird. So I can deactive Provider, I can't use Lightning, I can't use the email part of Thunderbird. Nothing.

When I delete / deactivate the addons via the secure mode, i can't make any modifications to them (so no calendar can be deactivated).

I will check the linked bug again and see if I overlooked anything.

OK, seems like I really overlooked something. After uninstalling Provider, but having Lightning still activated, there are still the Google Calendars. I am currently "unsubscribing" to them and will test now.

I use CalDav…

https://blog.mozilla.org/calendar/2013/09/google-is-changing-the-location-url-of-their-caldav-calendars/

OK, so I guess this was the problem. I deleted the calendars from Lightning and then added provider for google calendar manually, restarted and then added a few of the calendars (just to make sure). Seems to work so far with the fewer number of calenders. I will do some more testing and get back if there are more infos. Thanks for the help so far.