Hey!
I am running my own homeserver, Raspberrypi with Nextcloudpi installed, at home. Up until now I only ever clicked on the integrated letsencrypt plugin and it ran some commands in the background and my certificate was refreshed. Now it seems something changed but I didnt change anything in my setup.
I have my url cloud.joachimbergmann.de pointing to my myfritz.url.
The output nextcloudpi gives me:
letsencrypt ] (Sun Apr 7 12:21:07 BST 2024)
Saving debug log to /var/log/letsencrypt/letsencrypt.log
Plugins selected: Authenticator webroot, Installer None
Renewing an existing certificate for cloud.joachimbergmann.de
Performing the following challenges:
http-01 challenge for cloud.joachimbergmann.de
Using the webroot path /var/www/nextcloud for all unmatched domains.
Waiting for verification...
Challenge failed for domain cloud.joachimbergmann.de
http-01 challenge for cloud.joachimbergmann.de
Cleaning up challenges
Some challenges have failed.
IMPORTANT NOTES:
- The following errors were reported by the server:
Domain: cloud.joachimbergmann.de
Type: dns
Detail: no valid A records found for cloud.joachimbergmann.de; no
valid AAAA records found for cloud.joachimbergmann.de
It seems letsencrypt doenst like that my URL is pointing to the myfritz.url anymore? what do I have to do to get a running certificate from now on?
mind you, I am a beginner when it comes to domain-things, I was happy that I got it running in the first place. so be kind if I dont understand all of the terms being used 
Cheers from Berlin