Error 403 while uploading

while uploading from the nextcloud desktop app i keep getting error 403 forbidden to MKCOL. i am trying to upload mp4 files and pictures. while on my phone i can use the app for uploading for everything. Later on suddenly on de web-interface its saying :

Your data directory is not writable
Permissions can be restored by giving the root folder on the web server write access.

The folder already has root permissions.
And now i am unable to upload at all.

My nextcloud version is  24.0.3s.
OS is Ubuntu: 22.04.1 LTS (GNU/Linux 5.15.0-1013-raspi aarch64)

Does someone know how to fix this