Bizarre "Authentication Failed" Issue: Any OS permanently breaks if it EVER connects to my home network

[cagri.akman.kg]

Hi everyone,

I am in a desperate situation. I have 1 month left to finish my PhD, and since June 1st, I have been completely locked out of my university network due to a bizarre GlobalProtect issue.

I am consistently getting the "global protect authentication failed enter login credentials" error. I have tested every possible scenario, and the only common trigger is my home network. However, the issue is not a simple network block.

Here is my exact step-by-step troubleshooting log:

1. On June 1st, my main Windows 11 PC (which I always use) suddenly gave the "failed enter login credentials" error. 2. I tried installing GP with the same setup file on a second Windows 11 PC at home: It failed with the same error. Then, I used the exact same setup file on a remote Windows 11 PC that has NEVER been connected to my home network: It connected flawlessly. 3. I switched the two failing home PCs to three different mobile data hotspots. I tried resetting network adapters and flushed DNS/IP configs. The error persisted permanently on those devices. 4. At my workplace, I used a Mac that had previously connected to my home network in the past. I downloaded the installer via the work network and installed it: It failed with the same error. 5. At the exact same workplace, I installed GP on a Windows 11 PC that has never connected to my home network: It connected flawlessly. 6. Suspecting my home network, I installed an Ubuntu Virtual Machine on one of the failing home PCs. Using the open-source openconnect client on the active home network, I was able to log in perfectly. 7. I bought a brand-new Mac. Out of the box, I downloaded the installer via Safari on my home Wi-Fi and installed it: It immediately gave the "failed enter login credentials" error. 8. I tried another Mac connected to the home network: Same failure. 9. My Conclusion: This is NOT an ISP/Router block (because Ubuntu connects fine on the same network). This is NOT an OS issue (it happens on both Mac and Windows). The only logical conclusion: If a device has EVER connected to my home network, the GP client permanently breaks on that device.If it has never touched my home network, it works perfectly. 10. I have tried every uninstallation and cache-clearing method found on the internet. Nothing works once a device is "infected" by this state. 11. The University IT department checked their logs and confirmed there is no block or issue on their end. I also tested different valid usernames to download the installer; my credentials are 100% correct.

I am completely stuck. My router interface shows no blocks. I cannot rely on the Ubuntu VM workaround because transferring massive data files between the VM and my host machine for code analysis is absolute torture and practically impossible for my workflow.

What is happening to the GlobalProtect cache/registry when it touches my network? How can I completely eradicate this broken state from my devices?

I urgently need a fix. Any help is immensely appreciated.