Can't sync calendar

I am using eM client v 8.2.1237 (b402cf3) on Windows 10 Home (build 18363.1500).
I cannot sync my work calendar. It’s an exchange server. I can send and receive e-mails and I’m not having any problem synchronizing the calendar on my Galaxy S10 or my iPad. I get the following error message:

[Exchange Web Services]Synchronizing folder ‘email adress/Calendar’ failed due to the following error: The specified attachment Id is invalid.

Any idea? Without calendar access, eM client is useless to me.

There’s likely an event in your calendar which is improperly formatted and is blocking the calendar sync. It needs to be identified and deleted. Since you mention a work calendar, I’m assuming you have a pro version? If so, you can contact the pro support and they’ll be able to help you.
https://support.emclient.com/

Did the Pro support sort it out and how long did they take?

I submitted a ticket 4 weeks ago and have not received a reply.

There are no unanswered support tickets, Chris.

Can you please send me the ticket number, and I will look into it for you. gary@emclient.com