Gentlemen, for long time, I have been using eM Client, with great results.

For long time I have been enjoying eM Client with great results.
Recently I keep getting this constantat and annoying message:

Sychroniziing fowlder ‘Internet Calendars/http://example.org/calendar/’ failed due to the following error: The remote server returned an error: (404) Not found.

How can this be fixed?