Xbox 360 Live Sign-In Error 8015190A on Both Xbox 360 and Xbox Series X

Hello,

I'm experiencing a persistent Xbox Live authentication issue with my Microsoft account.

My account works normally on Xbox Series X, but whenever I try to connect to Xbox Live through the Xbox 360 system, I receive error code 8015190A.

This happens on two different consoles:

Original Xbox 360: Downloading my Xbox Live profile fails with error 8015190A.

Xbox Series X: Attempting to connect to Xbox Live inside a backward-compatible Xbox 360 game also produces error 8015190A.

Troubleshooting Already Completed

Tested my Xbox 360 network connection. Network, Internet, and Xbox Live all passed.

Tested my Xbox Series X using my home Ethernet connection with Moderate NAT.

Switched my Xbox Series X to a mobile hotspot with Open NAT. The error persisted.

Tried using a Microsoft account app password.

Confirmed that my Microsoft account signs in normally on Xbox Series X.

Confirmed that my Game Pass Ultimate subscription is active.

Checked Xbox network status, which showed all services operational.

Checked Microsoft account Recent Activity and found no failed sign-in attempts.

Confirmed that passwordless sign-in is disabled.

Changed the alternate network port without resolving the issue.

Important Finding

I tested a second Xbox account on the same Xbox Series X using the same mobile hotspot.

The second account successfully connected to Xbox 360 Live, while my main account continued to fail with error 8015190A.

This strongly suggests an account-specific Xbox 360 authentication problem rather than a network or hardware issue.

Additional Errors

During troubleshooting, I also encountered:

8015190E: Xbox 360 Live connection error.

0x80070525: Xbox 360 cloud storage unavailable.

My existing Xbox 360 game saves still load normally through backward compatibility.

What I Need Help With

Is there a known issue affecting Xbox 360 authentication for certain Microsoft accounts?

Could Microsoft investigate whether my account has a problem with legacy Xbox 360 authentication or profile synchronization?

I contacted Xbox Support, but the virtual assistant stated that live chat and phone support were unavailable for Xbox network sign-in issues.

I would appreciate assistance beyond standard network, password, and profile deletion troubleshooting, since I have already tested multiple consoles, connections, and accounts.

Thank you.