Hello ,
Good to see you in Microsoft Community.
Did you see the message "the account does not exist (not registered for the preview version)" in the Windows Insider Program interface in Windows Settings, or in the Microsoft Edge browser?
Usually, you can visit Leave the Windows Insider Program (microsoft.com) and log in to your Microsoft account that is already registered for the Windows Insider Program, then follow the prompts to opt out of the program. After that, you need to check in Windows Settings to see if these changes have taken effect.
Meanwhile, it indicates there might be an issue with the network connection between your computer and Microsoft servers (either it's slow or unable to connect). You can optimize your computer's connection to Microsoft servers by following the steps below. "Win" logo key + "Q" to open the search box, type 'ncpa.cpl', press Enter to open the "Network Connections" window, select your network adapter, right-click it > "Properties", double-click "Internet Protocol Version (TCP/IP)", then check “Use the following DNS server address", and*****type* "4.2.2.1" in "Preferred DNS server", and type "4.2.2.2" in "Alternate DNS server", then press OK*.*
If your other network applications fail to work properly (unable to load or slow connection) due to the above changes, you can set it to "Obtain DNS server address automatically" after the problem is fixed.
After exiting the Windows Insider Program, you can return to the stable version of Windows by clean reinstalling it. Alternatively, you can continue using the current version of Windows until the stable channel updates to the current version.
And you can visit How to clean install Windows 11 - Microsoft Community**** & How to: Perform a Clean Install or Reinstall of Windows 10 - Microsoft Community **** for specific installation steps.
If anything is unclear, please do not hesitate to let me know.
Best Regards,
Mosken_L - MSFT | Microsoft Community Support Specialist