Fresh Nextcloud install on upgraded system - 503 error

Hi,
I have upgraded Buster to Bullseye with a running dietpi system. The system has had a nextcloud service and a smb.
SMB kept on working, however nextcloud did not. Tried many thing, read lots of forums and decided to uninstall NC and hava a fresh install. After download however i can not reach nextcloud by <ip/nextcloud/> and have a 503 service unavailable error.
What did i do wrong?
thanks

all services are running?

dietpi-services status

Web server is reachable by it’s IP?

http://<ip>

Did you restored a backup or is it an empty installation?

yes

DietPi-Services
─────────────────────────────────────────────────────
 Mode: status

[  OK  ] DietPi-Services | nmbd                 : active (running) since Fri 2021-09-24 11:11:02 BST; 23min ago
[  OK  ] DietPi-Services | smbd                 : active (running) since Fri 2021-09-24 11:11:03 BST; 23min ago
[  OK  ] DietPi-Services | redis-server         : active (running) since Fri 2021-09-24 11:11:03 BST; 23min ago
[  OK  ] DietPi-Services | mariadb              : active (running) since Fri 2021-09-24 11:11:05 BST; 23min ago
[  OK  ] DietPi-Services | php7.4-fpm           : active (running) since Fri 2021-09-24 11:11:07 BST; 23min ago
[  OK  ] DietPi-Services | lighttpd             : active (running) since Fri 2021-09-24 11:11:08 BST; 23min ago
[  OK  ] DietPi-Services | cron                 : active (running) since Fri 2021-09-24 11:11:08 BST; 23min ago
[  OK  ] DietPi-Services | dropbear             : active (running) since Fri 2021-09-24 11:11:01 BST; 23min ago
[  OK  ] DietPi-Services | fail2ban             : active (running) since Fri 2021-09-24 11:10:48 BST; 23min ago
[ INFO ] DietPi-Services | dietpi-vpn           : inactive (dead)
[  OK  ] DietPi-Services | dietpi-ramlog        : active (exited) since Fri 2021-09-24 11:10:39 BST; 23min ago
[  OK  ] DietPi-Services | dietpi-preboot       : active (exited) since Fri 2021-09-24 11:10:39 BST; 23min ago
[  OK  ] DietPi-Services | dietpi-boot          : active (exited) since Fri 2021-09-24 11:11:00 BST; 23min ago
[  OK  ] DietPi-Services | dietpi-postboot      : active (exited) since Fri 2021-09-24 11:11:00 BST; 23min ago
[ INFO ] DietPi-Services | dietpi-wifi-monitor  : inactive (dead)

yes it is reachable

new installtion, backup was not used

what about the error log

cat /mnt/dietpi_userdata/nextcloud_data/nextcloud.log

shows nothing…the command returns nothing

{“reqId”:“Y9i8QNVwEPerCzPh1UZ9”,“level”:3,“time”:“2021-09-24T11:20:03+00:00”,“remoteAddr”:"",“user”:"–",“app”:“PHP”,“method”:"",“url”:"–",“message”:“Trying to access array offset on value of type null at /var/www/nextcloud/apps/dav/lib/CalDAV/BirthdayService.php#306”,“userAgent”:"–",“version”:“22.1.1.2”,“exception”:{“Exception”:“Error”,“Message”:“Trying to access array offset on value of type null at /var/www/nextcloud/apps/dav/lib/CalDAV/BirthdayService.php#306”,“Code”:0,“Trace”:[{“file”:"/var/www/nextcloud/apps/dav/lib/CalDAV/BirthdayService.php",“line”:306,“function”:“onError”,“class”:“OC\Log\ErrorHandler”,“type”:"::"},{“file”:"/var/www/nextcloud/apps/dav/lib/BackgroundJob/GenerateBirthdayCalendarBackgroundJob.php",“line”:69,“function”:“resetForUser”,“class”:“OCA\DAV\CalDAV\BirthdayService”,“type”:"->"},{“file”:"/var/www/nextcloud/lib/private/BackgroundJob/Job.php",“line”:51,“function”:“run”,“class”:“OCA\DAV\BackgroundJob\GenerateBirthdayCalendarBackgroundJob”,“type”:"->"},{“file”:"/var/www/nextcloud/lib/private/BackgroundJob/QueuedJob.php",“line”:45,“function”:“execute”,“class”:“OC\BackgroundJob\Job”,“type”:"->"},{“file”:"/var/www/nextcloud/cron.php",“line”:127,“function”:“execute”,“class”:“OC\BackgroundJob\QueuedJob”,“type”:"->"}],“File”:"/var/www/nextcloud/lib/private/Log/ErrorHandler.php",“Line”:92,“CustomMessage”:"–"}}

hmm there seems to be an issue with CalDAV. At least some errors generated by CalDAV/BirthdayService.php

{"Exception":"Error","Message":"Trying to access array offset on value of type null at

And you are sure it was an empty installation? Nothing got imported during install?