Defender for iOS: “This account has reached its devices limit” even though no devices are listed

• I am using all 5 devices available (2 PC's, 1 Mac, 2 IOS devices)
• I was trying to install Microsoft Defender for IOS on a new iPhone created by copying from the old phone (iPhone 11) to the new phone (iPhone 17).
• I erased my old iPhone 11 while Defender was still installed
• My Microsoft account shows zero mobile devices (none were linked to my MS account)
• Defender on the new iPhone never completed sign‑in with my MS account
• “Sign out everywhere” and app removal didn’t help (also app removal, restart IOS device, reinstall Defender for IOS)
• You suspect a stuck Defender mobile enrollment token
• You need Microsoft to reset the backend mobile device slot

From Office Copilot:

What to tell the agent (so you don’t get bounced)

Use this exact wording:

“Microsoft Defender for iOS says ‘This account has reached its devices limit’ even though no devices appear in my Microsoft account. My old iPhone was erased while Defender was still signed in. I need my Defender mobile device enrollment reset.”

This sends them straight to the backend reset tool.

Why this works when everything else doesn’t

The issue isn’t on your devices or in your account UI — it’s a server-side Defender mobile quota flag that only Microsoft support can clear. The consumer Defender team (under Microsoft 365 support) is the only group with access to that system.