"Problem occured while adding event" in Zoho Mail

I've received several webinar invitations where the .ics calendar file is attached to the e-mail. In Zoho Mail, I'm presented with the option to "Add Event," but when I click it, I get the following error notification (see attachment as well): "Problem occured while adding event."

Attached is the e-mail header and I've left the e-mail in my inbox in case that is of any assistance to you.

Update: I've noticed that the event is successfully created in my calendar, despite the error.