What is going on???
Sorry you ran into difficulty. Unfortunately, unless you fill out the support template no one here will have the necessary details to provide you with any assistance. There are numerous possibilities and variables.
I had to get a server admin to fix it last time and now I’ll have to do it again.
Self-hosting means you’re the server admin. For those that don’t wish to be their own server admin, however, there are third-party managed hosting solutions for Nextcloud.
Generally the server admin is the party that performs the upgrades due to the nature of Nextcloud. It’s not a typical consumer/web app.
If you have to get a server admin involved to fix things, make sure they are comfortable/acquainted with the specifics of Nextcloud Server administration. And also that they are able to either isolate the root cause (to avoid future occurrences!) and/or are at least willing reach out here with the appropriate details to try to get assistance.