What versions of Seafile Server and Client are you running? Is this the Sync client or the Desktop Drive client?
Assuming you are running a newer version of Seafile server, I would completely uninstall the client software using something like AppCleaner. You can also do it by hand if you prefer.
Next, reinstall the client software using the latest release. You can download the installer here.
I’ve seen this kind of problem several times under varying circumstances and there are reports of its treatment recorded on this forum. For example, here’s an example of a complete uninstall of SeaDrive on a Mac that might help.
While it might seem a bit drastic or too much work, I have not seen this approach fail.
Give it a try and please report back what you see.
Good luck!