You can open about:sync-log via the location bar to see if recent Sync logs are available. You can upload the file to a website like Pastesite if you can't post the content of the file in a reply.

• https://pastesite.org/

You can temporarily toggle this pref to true to get a Sync log in case of success to check how Sync performs.

• services.sync.log.appender.file.logOnSuccess = true

Do not forget to reset services.sync.log.appender.file.logOnSuccess after you are done testing.

You can open the about:config page via the location/address bar. If you get the warning page, you can click the "Accept the Risk and Continue" button.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

You can open about:sync-log via the location bar to see if recent Sync logs are available. You can upload the file to a website like Pastesite if you can't post the content of the file in a reply.

• https://pastesite.org/

You can temporarily toggle this pref to true to get a Sync log in case of success to check how Sync performs.

• services.sync.log.appender.file.logOnSuccess = true

Do not forget to reset services.sync.log.appender.file.logOnSuccess after you are done testing. You can open the about:config page via the location/address bar. If you get the warning page, you can click the "Accept the Risk and Continue" button.

• https://support.mozilla.org/en-US/kb/about-config-editor-firefox

I'm not sure I understand. When I go to about:sync-log, nothing is there.

By default will Firefox only create a sync log (error-sync-xxxxxxxxxxxxx.txt) if there has been an error with Sync, so if the about:sync-log is empty then everything is OK and there haven't been errors. The logOnSuccess pref I mentioned above allows to create a log every time Firefox performs a sync to allow you to check the progress. If you set that pref to true then you should always reset the pref to false once you are done testing how Sync performs to prevent Firefox from filling up the Crash Reports folder with success-sync logs.