Unable to Sync Joplin Notes with Mailbox.org via WebDAV

I’m trying to sync the Joplin notes application with mailbox.org using WebDAV. Since I use 2FA, I’ve created an application password and configured the WebDAV URL as follows:
https://dav.mailbox.org/servlet/webdav.infostore/

In Joplin, the sync configuration check returns a success message:
“Success! Synchronization configuration appears to be correct.”

However, when I attempt to sync my notes, I receive the following error:
“Last error: Error: MKCOL locks/: Access denied: Please check your username and password (403):”

I reached out to mailbox.org support, and they suggested posting here. Has anyone else set up Joplin with mailbox.org or experienced this issue? If so, I’d appreciate any advice or insights.

Thank you!