I use Joplin 2.7.2 on my android phone and sync via pcloud (webdav).
I also use Joplin on two computers and had the sync working on all three devices. Recently, I had sync issues with my phone and reinstalled Joplin on my phone.
On my pcloud, I sync with a subfolder. If I put the URL with the subfolder in the sync-settings, I cannot sync any notes, but get the error:
Error: PUT .resource/xxx: Unknown error 2 (403): 403 Forbidden
Forbidden
Forbidden
>You don't have permission to access this resoure.
If I then delete the subfolder from the URL, I am able to sync (after the sync-target is being upgraded) but then I can only sync the new notes.
I had recurring issues with pCloud's WebDAV, increasing with the number of notes. Forbidden permissions was one of the issues for me as well. pCloud support was of little help. Their implementation of WebDAV seems defective. I was hoping to save on the sync hosting cost, but eventually switched to Joplin Cloud. It's great and I feel good supporting this open source app.