Once in a while you Google on some error and come across an old blog post of yours … and you smile. :) That’s what happened today. I was trying to Backup-GPO and Restore-GPO between two (trusted) domains and got the above error. Turns out this is expected when restoring GPOs between domains and I had encountered it previously. The workaround is to make a new GPO in the target domain and import the settings from the backed up GPO.
You can either do this via PowerShell – use the Import-GPO cmdlet, or via GPO – right click the GPO and select “Import Settings”.
Funny, the post I found was from 6 years ago … had forgotten I used to play with this stuff back then too.