Enter about:sync-log in the url bar and check if there any error files. This file should contain the reason of not syncing.

TyDraniu said

Enter about:sync-log in the url bar and check if there any error files. This file should contain the reason of not syncing.

No log at all

Did you by any chance changed the password of the Sync account?

If you change the password for the Sync account then all data stored on the Sync server is removed.

cor-el said

Did you by any chance changed the password of the Sync account? If you change the password for the Sync account then all data stored on the Sync server is removed.

Nothing was changed, just had to wipe the system drive and reinstall everything. Firefox account password was not touched

Hi

Thank you for your question about the Firefox Sync service.

It appears from your question, that you are using Firefox Sync as a back up service. This is not what Sync is designed to do. The Firefox Sync service takes a copy of the data you wish to include and transfers it to a second device (typically a mobile device such as a tablet or a telephone) running a copy of Firefox. The storage in between all attached devices is both temporary and fragile and is not stable enough to be (and is not designed as) a reliable backup service.

If you have a copy of your Firefox profile for desktop Firefox, you may be able to recover your bookmarks and other data. Please have a read of this article.

If you have a copy of your data on a mobile version of Firefox, please follow these instructions to connect it to Firefox Sync to copy your data.