Shared Calendar Not Loading Events for Corporate User

Hi. I am hoping its possible to get some assistance/guidance. Here is the short of the situation:

Our team is developing an Add On for Microsoft Outlook that connects with our pre-existing custom solution that uses GraphQL endpoints. This solution allows our clients to schedule, edit, cancel, and invite participants to events. Our team has requirements surrounding this issue: we don't want to be able to read the users' entire calendar/email as it makes us a potential breach point for them. We only want read/write access to a special calendar for our custom solution events.

We have created a special calendar for our users to use but we are having issues with users seeing events on that calendar, particularly when the users are corporate/enterprise users. I'm trying to figure out where and why this error is occuring.

Does anyone have information on this? Or direct me to where I should ask this question?