I recently helped a friend of mine to install GP on his laptop (he’s planning on buying GP) and ran into this also. It’s a security measure, which is now by default set to rather strict. I think Microsoft changed this to improve security.
Edit:
This should change the policy temporarily to execute the script once:
Set-ExecutionPolicy -ExecutionPolicy Unrestricted -Scope Process
The following command would change the policy permanently (hence the more restrictive RemoteSigned) for the current user:
Set-ExecutionPolicy -ExecutionPolicy RemoteSigned -Scope CurrentUser
RemoteSigned means that scripts not on the local computer don’t run. Scripts that are downloaded from the internet need to be unblocked:
Unblock-File -Path <script.ps1>