Nexcloud 21.0.3 snap1 - cannot start

I have Ubuntu server 20.04.2 + snap installation of Nextcloud 21.0.3 Snap1.
Today we had a power failure and I am not able to start the Nextcloud server.

There is running Nextcloud Maintenance mode after the reboot of the Ubuntu server for few minutes. After that, I receive " Page is not available".

SSH access to the Ubuntu server is working fine.
How can I fix it?
Thank you very much for your answer.

Please log an issue over on the snap, we have a nice log-gathering script there that will help us figure out what happened. My first guess is that MySQL got corrupted.