Thanks for letting us know. I'm here to guide you to the right support and make sure you'll get the best help with the error you're getting.
I appreciate your effort in providing me the detailed information and the steps you've processed just to sort out this issue. Since you've followed all troubleshooting steps and the problem still persists, I encourage you to contact our QuickBooks Desktop Technical Support Team. They have additional tools to pull up your account in a secure environment and do a remote session to investigate this further.