hi, which isp are you using?

Hi philipp, I'm on cable ISP called Unitymedia (in Germany ;) )

How long did you let the initial Sync run on that new installation? Maybe it needs more time.

Also, you can check about:sync-log (typed in the URL bar) to see if there are any sync error reports saved.

If so copy & paste the report to - http://pastebin.mozilla.org/ - and post the resulting URL to this forum. Make sure you select "a month" for retention of that "paste", as "a day" usually isn't long enough especially leading into a weekend.

thanks, then it's likely that you are experiencing a bug with the unitymedia ds-light network: https://bugzilla.mozilla.org/show_bug.cgi?id=1118958 - for a workaround see comment #19 there.

How long did you let the initial Sync run on that new installation? Maybe it needs more time. Also, you can check about:sync-log (typed in the URL bar) to see if there are any sync error reports saved.

Hi the-edmeister, thanks for your answer. Of course I gave Sync enough time to do the initial sync. I think 5 days (more or less without turning my Laptop off) should be more than enough ;)

I looked at about:sync-log (which I didn't know before your post) and there are several error logs since... 5 days :P I won't post a log now, because philipp gave a great hint...

for a workaround see comment #19 there

Since I don't know what to replace e.g. "what:ever/128" to, I read some comments below on that page and [comment 27] said to set "sysctl -w net.ipv4.tcp_mtu_probing=1" [in terminal], which worked flawlessly and after a Firefox restart, Sync started immediately. Even if I don't really know what that setting does... xD

Now I have all my bookmarks, passwords etc. synchronized.

Thanks to both of you!

If anyone wants me to provide a sync error log, when net.ipv4.tcp_mtu_probing was set to 0, I will post it to try to help fixing that bug(? If it can be fixed).