See my response here. It is a limitation by Samsung who most likely do not want us to download their app from Google Store.
I am also looking for this solution. In my situation, the company setup a work profile with our Outlook and other company configured and approved applications (e.g. Teams, O365, Zoom),on my enrolled Samsung S8 phone. This allows me to fully operate the phone in either personal or work modes. I just got the Watch3 and setup notifications and Outlook, I get both personal and work email on my watch but the calendar is not letting me add my outlook calendar from my work account? I am getting blocked at enrollment although, the email is working. Is this similar to your situation or are you using the Google calendar as suggested below?