Make sure you are not blocking content.

https://support.mozilla.org/en-US/kb/enhanced-tracking-protection-firefox-desktop also see https://blog.mozilla.org/security/2021/03/23/introducing-smartblock/

https://support.mozilla.org/en-US/kb/smartblock-enhanced-tracking-protection

Diagnose Firefox issues using Troubleshoot(Safe) Mode {web link}

A small dialog should appear. Click Start In Troubleshoot(Safe) Mode (not Refresh). Is the problem still there?

Many site issues can be caused by corrupt cookies or cache.

Warning ! ! This will log you out of sites you're logged in to. You may also lose any settings for that website.

• Delete cookies to remove the information websites have stored on your computer {web link}

• How to clear the Firefox cache {web link}

We aren't blocking anything - whether I clear cache or not, I can get logged in and navigate around a bit. After I arrow back, it quits loading. However, if I use a private window it doesn't seem to have the issue.

Note: Some add-ons are not active when using Private Browsing unless you set them up that way.

Also, when using Private Browsing: cookies, cache, and all other data are saved to temporary files that are removed when the browser is closed.

Delete browsing, search and download history on Firefox {web link}

Remove a single website from your history {web link}

Open the History Manager <Control> (Mac=<Command>) <Shift> H. In the search bar, enter the name of the site. Right-click on one of the listings and select Forget About This Site. This should remove all information, including any site settings And Passwords.

Our business is also having the same issue with 99 and now 99.1 Sharepoint sites on the loading screen. Other browsers do not have the same issue. Cache has been cleared, everything works fine on version 98.

Crtl + f5 helps temporarily.

It appears that it's an issue with any website that uses MFA.

Our business is having this issue as well. Firefox 99 and 99.0.1. Sharepoint sites sit and load continuously until you clear site cache or Control + F5. This only works for a little while before it needs to be refreshed again. Versions before 99 work just fine.

We are also having this issue. Refreshing Firefox takes care of the issue but only for a little while, then issue resumes. Will load every time on a cntl - F5

A coworker of mine found this and it appears to be working: set dom.serviceWorkers.navigationPreload.enabled to False

There are two workarounds:

1. Yes, going into about:config and setting dom.serviceWorkers.navigationPreload.enabled from true to false resolves the issue. Although this may be a workaround for SharePoint, folks should be mindful that this setting might impact other websites.

2. Another workaround would be to use Firefox in a private browsing session.

This seems like a Firefox regression related to the newly added service worker navigation preload support.

SharePoint Online service alert

Advisory information Title: Users can't load modern SharePoint Online sites when using the Firefox browser ID: SP357692 Status Service Degradation Details Title: Users can't load modern SharePoint Online sites when using the Firefox browser User Impact: Users are unable to load SharePoint Online modern sites when using the Firefox browser. More info: Users can load modern sites with private browsing in Firefox or use any other web browser. Current status: We've identified a navigation preload problem that is affecting users attempting to load modern sites with the Firefox browser. We're developing a fix, designed to circumvent the navigation preload problem, which is expected to remediate impact. Scope of impact: This issue may impact any user attempting to load SharePoint Online modern sites when using Firefox browser versions 99.0 and above. Root cause: A navigation preload problem is preventing users from loading SharePoint Online modern sites when using the latest versions of the Firefox browser. Next update by: Tuesday, April 12, 2022, at 11:00 PM UTC Are you experiencing this issue? Thank you, The Microsoft team

A fix has been deployed to all SharePoint users. The SharePoint service worker mitigated the issue by reverting to using standard fetch instead of native navigation preload if the browser is Firefox.

Note that you may need to clear the browser cache and restart the browser for the fix to take effect.

Firefox navigation preload can hopefully be re-enabled soon - once the root cause has been determined and addressed.