How do i let external O365 accounts using my multi-tenant app?

Question

We provide a SaaS solution for managing appointments. Many of our clients want to connect their Office 365 accounts to our platform.

The functionalities we aim to implement are:

• Connecting an account from our software to an Office 365 account.
• Syncing data through the API to Office 365 when someone books an appointment.
• Updating data through the API to Office 365 when someone edits an appointment.
• Retrieving data from Office 365 through the API to block the timeslot in our software when there is an appointment in Office 365.

We have developed all these APIs and tested them with our own Office 365 accounts, and they work correctly.

We registered the application as a multi-tenant app. However, external users encounter an error when trying to use it. We have discovered that we need to add an MPN ID.

We are currently stuck at this point. Can anyone help?

We registered the application as a multi-tenant app. However, external users encounter an error when trying to use it. We have discovered that we need to add an MPN ID.

We are currently stuck at this point. Can anyone help?