M365 March 2021 Update
You must update your M365 App Registration Redirect URLs by 24th March 2021
The change must be made to ensure continuity of service for the Microsoft 365 Marketplace integrations.
The new Redirect URI needs to be in the following format:
Redirect: https://{intranet-domain}/marketplace/microsoft/account/sign-in/oauth2
eg.
Redirect: https://intranet.acme.com/marketplace/microsoft/account/sign-in/oauth2

Full setup instructions (including the above change) can be found here.
Updated about 1 month ago