i'm baffled here. decomm'd old cloud connectors and populated HKLM\Software\Policies\Citrix\VirtualDesktopAgent (ListOfDDCs) via GPO and the VDA is still trying to register with the old entries in this key. i can't figure out where the VDA is hanging on to the old entries. VDA 2402

Are they persistent? Set the Enable Auto Update of Controllers to Prohibited. On a persistent machine once the list of controllers is cached the VDA will not look at the list of DDCS again it just uses the cached list. This will tell it to use the list of ddcs again

They're MCS provisioned non-persistent.

could you have gottne the list cached in your master image? Try the policy anyweway if its somehow cache it will still work for you

Try this. I've never experienced this, but it's in my troubleshooting notes: https://support.citrix.com/s/article/CTX216883-vda-attempting-to-register-to-an-old-or-decomissioned-ddc-after-upgrade?language=en_US

Decomm done in Citrix Cloud as well (resource location)? Make sure zones etc are all correct - I've had VDAs boot and look for the wrong Cloud Connector due to incorrect zone information configured for the catalog.

There's an XML file I think under C:\ProgramData somewhere that you need to remove, let me try and find it Edit - it's the one referenced in Jeremy's article link. I've come across this a number of times.