An error occurred, unable to create the calendar

Installed a fresh NC 26 instance using nextcloudpi. It seems to work, but when I try to create a calendar I get the error

An error occurred, unable to create the calendar.

In my browser dev tools I see a 503 code. The log file doesn’t provide any additional information.

I edited (in nano) config.php

  'logfile' => '/opt/ncdata/data/nextcloud.log',
  'loglevel' => 3,

tried all loglevels from 3 to 0. No change. Is that the correct way to change the log level? Any other logfiles?

The webserver log file or nextcloud.log log file?

nextcloud.log, did a tail -f on it, but no changes on it.

I did another test. In total I did 3 fresh installs, 2 with the result above. Now I did one install which worked, where I had the following difference to the failed tries:

a) Before I activated my NC instance I added my machine real host name to the white list of NC and did the activation using this hostname.

sudo -u www-data php /var/www/nextcloud/occ config:system:set trusted_domains 9 --value=myrealhostname

b) When calling next cloud the first time (before I hit the activate button) the browser shows me to ncp users with generated passwords. I have to admit I am confused what the difference between these two ncp users are since it says that for both users the user name is “ncp” and one is for next cloud and one for next cloud pi. I have ignored these two users and used

sudo ncp-config

to set a password for the user ncp. That password I have used for the very first logon.

Does that give some indication what went wrong? Though the third install looks somewhat good for now, I still would like to know/understand/learn for the next occurrence…