Artifact Signing organization verification: "You need permission" (Microsoft Accounts tenant) for a personal Microsoft account owner

I have a Public organization identity validation for Azure Artifact Signing in status "Action Required". The verification link (from the portal and from the email) opens credentials.microsoft.com and shows "You need permission". The page says I am signed in on the tenant "Microsoft Accounts" instead of my own Entra directory.

Setup:

• The Azure account was created with a personal Microsoft account. That account is the subscription Owner and appears as a Guest (#EXT#) in the directory.
• The account has the Artifact Signing Identity Verifier role (on the resource group that holds the signing account).
• The primary email on the validation request is the same address as the account I sign in with.

What I tried:

• The link from Identity validations in the portal, and the link from the email.
• A private browser window, with the portal opened on the directory's own address.
• "Sign-in options > Sign in to an organization" with my onmicrosoft.com domain. That ends in an endless "Redirecting to Login page...".

I have no paid support plan, so I cannot open a technical support request. Can a Microsoft employee please check the tenant binding of my validation request? I can send the validation ID, tenant ID and subscription ID privately. I am worried that the 7-day link expires.