Hello,
It might sound obvious, but did you indeed check that the nextcloud is reacheable?
Some tests to do off the top of my head:
- there's no system proxy,
- the Nextcloud password is non blank,
- the webdav url is correctly copied from nextcloud interface,
- Joplin button Test connection gives positive result
There's pretty much no help that would replace you personally poking around at the problem. Keep us posted
Here a topic tackling with similar problem:
Best of luck