Appointment App not working

[hokaido]

Installed appointment app, but only get this error:

internal server error

The server could not complete the request.

If this occurs again, please send the following technical details to your server administrator.

Further details can be found in the server log.
Technical details

Any ideas how to solve?

Thanks

[tcit]

Check your nextcloud.log file and report an issue to https://github.com/SergeyMosin/Appointments/issues