Apple Calendar not synching some accounts on desktop but syncs on iPhone

This is a previous post made by jimfromsouthold. This exact thing has been happening to me for months and it doesn't seem like it was solved yet so I wanted to repost this problem. I edited his post a little to make the details more relevant to my situation.

When I add new internet accounts to my iPhone, it syncs seamlessly. The mail app, iCal, contacts all sync. However, two of my accounts are not showing up on my laptop in the iCal app. Both devices have the latest iOS, I have the iPhone 12 mini and MacBook Pro. I've tried deleting the account and then enabling again, with no success. In fact, now one account no longer even shows a checkbox on the calendar. They are both school related Microsofts accounts. Any guidance would be much appreciated. Thanks in advance!