Invitations are blocked for this directory due to suspicious activity – small production tenant, need unblock

Hello,

Our Microsoft Entra ID tenant is unable to send any B2B guest invitations. Every attempt, including from a Global Administrator, fails with:

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

Details:

• First observed: 2026-09-25 08:57 UTC
• API: Microsoft Graph POST /invitations (via Microsoft.Graph SDK)
• Tenant size: 16 users total, 3 app registrations, Entra ID Free
• Use case: production SaaS application for tax accounting firms in Japan. Guest invitations are used only to provision customer staff accounts, one at a time, from our backend. No bulk invitations.

We have verified this is not a cross-tenant access or external collaboration setting issue, and not a per-user permission problem. It appears to be a directory-level protection block.

We opened an Azure support request (case 2609250060001777) but it was closed because our subscription is on the Basic plan, which does not include technical support. We are a small team and cannot purchase a paid support plan at this time.

No customers are affected yet, but we expect to onboard new customer staff within the next couple of weeks, and we will not be able to do so while this block is in place.

From similar threads here, I understand a Microsoft moderator may be able to help get the tenant reviewed and unblocked. I can share the tenant ID and business justification privately (e.g. via azcommunity email) as instructed.

Could someone please advise on how to get the block removed?

Thank you.