Hey @RolandKwee, welcome to the Nextcloud community and thanks for supporting Nextcloud snap 
Sorry to hear you are having issues with your Nextcloud snap installation. If you’ve come this far, you’re on the right track! There is a good chance someone in the community has had a similar issue and knows how to resolve it.
In order to help you we’ll need some Information to get an Idea of your setup, so complete the required support template and post the output of the following command allowing us to look at your redacted configuration file:
sudo nextcloud.occ config:list
Nextcloud logs are very verbose, thus your logs will certainly help resolve your issue. access your logs by following how to manage Nextcloud snap logs or you could run the debugging script and post the result here or paste the result of the following command:
sudo tail -n 20 /var/snap/nextcloud/current/logs/nextcloud.log
Below are some links to how-to’s answering frequently asked questions and may help you help yourself;
- How to install Nextcloud snap
- How to configure Nextcloud snap
- How to edit config.php for Nextcloud snap
- How to use OCC management console for Nextcloud snap
- How to revert Nextcloud snap after failed update
- How to manage failed automatic update in Nextcloud snap
- Nextcloud snap wiki and support
pay special attention to https://github.com/nextcloud-snap/nextcloud-snap/wiki/Putting-the-snap-behind-a-reverse-proxy
you’ll find that NGINX reverse proxy, especially NGINX Reverse Proxy Manager (NPM) reserves port 80 and port 81 for itself… thus your snap and NPM will be trying to use port 81 in your case.
it may help to expose the snap on another port like port 82 see HTTP/HTTPS port configuration see also NGINX proxy manager · nextcloud-snap/nextcloud-snap Wiki · GitHub