B2B guest invitations are blocked for this tenant due to suspicious activity

Hello Microsoft Support,

We are experiencing a critical issue with B2B guest invitations in our Microsoft Entra ID tenant.

As part of a legitimate customer onboarding / SSO rollout, we invited a large number of external users for our client organisation. After this bulk onboarding, new B2B guest invitations started failing.

Microsoft Graph now returns:

{

"error": {

"code": "Forbidden",

"message": "Invitations are blocked for this directory due to suspicious activity. Please contact Microsoft support for help."

}

}

Manual invites in the Azure / Entra portal also fail with:

"User invitation failed. Insufficient privileges to complete the operation."

This happens even when using a Global Administrator account. We have also checked External collaboration settings:

• guest invitations are enabled
• invitations are allowed to any domain
• the affected domains are not blocked

Context:

We are the Global Administrators for this tenant. The invitations were part of a legitimate production customer rollout. The users are legitimate customer users who need access to our application via SSO.

Impact:

• We can no longer invite new B2B guests.
• Some legitimate customer users cannot access our application via SSO.
• This is affecting an active customer rollout.

Request:

• Please review and remove the "suspicious activity" block on our directory's B2B invitation capability.
• Please confirm any guidelines or best practices to avoid hitting this block during legitimate customer bulk onboarding.

We can provide the Tenant ID/domain, Global Administrator email, Graph request IDs, timestamps, and business justification privately if needed.

Thank you.