Thank you! I didn't know about this way to set up syncing and now all my installs are syncing.
To answer your questions.
Does the entire Joplin window disappear?
No it wasn't the entire Joplin window, just the sync wizard window.
After clicking login, the sync wizard would just disappear and nothing would happen.
Does this also happen after clicking "Check synchronisation configuration"?
Using the "Check synchronisation configuration" has worked all but one of my installs, so thank you. On my work laptop I add proxy & cert setting but after that it worked.
Extra context, I original tried sync wizard on my work laptop and then on multiple personal devices. So don't know if its possible that because the proxy wasn't set on the first device that messed something up breaking the wizard on any other install.
Here is the error message I get with out proxy & cert settings
Error. Please check that URL, username, password, etc. are correct and that the sync target is accessible. The reported error was: request to https://api.joplincloud.com/api/sessions failed, reason: connect EACCES 13.38.116.178:443 (Code EACCES)