Hi There, Trying to sync event series but when I click the calendar logo next to the related Salesforce record

Trying to sync event series but when I click the calendar logo next to the related record, I get he message: “First sync the series to salesforce”, but then how do I do that?

Btw, I have made sure that my ‘sync recuring event’ checkbox in data set it checked.

Thanks for any help in clearing this up.