After migrating from Intermedia to Microsoft, user's calendar not syncing with Google

We migrated a client from Intermedia to Microsoft. So far so good until a client said they tried sharing their calendar to their Google account because they track some specific thing, doesnt matter, but the calendar doesnt update.

I've tried adding the calendar on my personal Exchange to Gmail, and it too doesnt work.

I got to OWA > settings > Calendar > Shared Calendars and publish the calendar. Then copy the ics link to google. It adds the calendar but there are no updates.

I tried sharing the calendar but the gmail account just gets an outlook link to open so that doesnt work.

Client has always been able to do this before moving to M365. What options do I have?