Help! Error CalDAV

Please help, what can I do I keep getting these errors and I already have the latest version of eM Client 9.0.1708 ?

Or can someone tell me how to disable this?

[CalDAV] Sync of XXXXXXXXXX@yahoo.co.uk/XXXX XXXXX failed due to the following error: XXXXXXXXX@yahoo.co.UK (internal error - server connection terminated)