Exchange calendar has stopped syncing on MacBook

I have an iMac, MacBook Pro and iPhone.

I use a company exchange (office365) account.

Only the calendar that is part of the exchange account has stopped syncing. The other calendars work.

I have tried several things to get it to work, but I cannot fix it.

It doesn't sync both ways: new entries don't show up on the other devices, the calendar doesn't receive updates.

With iPhone, iMac, everything is in sync.

I've disabled the account, I've tried to do a manual refresh, I've changed the setting from push to automatic refresh every minute. To no avail.

If I try to remove the account, it warns me that it will remove the account from all my computers which use the iCloud keychain (and I don't want that obviously).

Anyone a suggestion?