When you connect your Outlook Calendar to Bubbles, you might see a screen like this:

This means your organization does not allow third-party apps without approval from an admin within Microsoft 365. To resolve this, you will need to contact an admin and ask them to approve it. Here are instructions from Microsoft on how they can do that: https://learn.microsoft.com/en-us/entra/identity/enterprise-apps/review-admin-consent-requests

In our case, we found that article to be outdated at the time of writing (March 26th, 2024). Here is the direct link we see working today: https://entra.microsoft.com/#view/Microsoft_AAD_IAM/StartboardApplicationsMenuBlade/~/AccessRequests