Problem by changing the URL:
I changed the URL to another URL which is used with Joplin on other devices. Now Joplin synchronizes only new notes but not the older already existing notes.
I had to uninstall Joplin and delet the old directory: user/appdata/roaming/Joplin. Now I reinstalled Joplin and everything worked fine.
Is there another way to change the URL to an existing instance of Joplin which is less complicated?
Which url did you change?
The webDAV-URL from a nextcloud-Server.
Ok