Hello @CHRIS PORTER,
Below is the resolution from OP ( CHRIS PORTER,), posting it as an answer so that it is helpful to other readers with similar issue.
Sorry, yes. I eventually moved the workspace to another region and got it to work.
I'm sorry to hear that you are experiencing issues with starting a Data Flow Debug in US West 3. There could be several reasons why the debug session is failing to start, including permission issues, network connectivity issues, or service outages, looks like you have all permissions on the resources!!!
Did you try to deploy and use in other regions?
Any screenshot of the error?