MKCOL error

Joplin is being used on two Linux Mint desktops and two Android devices. Lately, this error message has been appearing below the Synchronization button on each device:

Last error: Error: MKCOL .sync/: Unknown error 2 (403):

It was ignored at first but it is now seen that the devices are not syncing correctly. What can be done, please?

If you search for “MKCOL” or “403” here and on the GitHub repo, there are several results. Do any of these help?

Yes, thank you, I did search for MKCOL and 403 as you suggested, but didn’t find any useful leads.
However, after three weeks of seeing these error messages daily, I’m delighted to report that the issue has today, without any input from me, spontaneously and mysteriously fixed itself! The error messages have disappeared and all entries have been fully updated on all four devices!