Windows 10 desktop app: sychronisation is disabled

I have installed the desktop app on Windows 10. The icon is grey with vertical bars. The tooltip says “Account synchronisation is disabled”.

I have uninstalled and reinstalled it, reconnected to my hosted account each time. This has not helped.

So, is this a problem with:
a) me
b) the desktop app
c) my Nextcloud host?

And how can I fix it…

Answer: it was a server configuration thing. It got fixed within minutes of me reporting it.

Everything works as it should now.