Nextcloud macOS app fails to launch

I have Nextcloud running and installed the sync app on my macOS laptop.

It started syncing and froze so that I could not move the window or cancel its operations.

I rebooted but now the app refuses to launch. When i look in the macOS Activity Monitor I see the Nexcloud App and the headless nextcloud agent.

I have tried removing the app entirely, rebooting (no Nextcloud stuff running), and reinstalling but I can never get the GUI for Nexcloud sync app to launch now.

Any ideas how to get out of this situation?