Outbound campaign 422 error on list assignment via CLI in AU-1

Struggling to figure out why the CLI throws a 422 Unprocessable Entity when assigning a contact list to an outbound campaign.

Environment: Genesys Cloud CLI v2.1.0, AU-1 BYOC.
Action: Automating campaign setup via GitHub Actions. The contact list exists and is valid. The campaign resource is created, but the association fails.

Error: “List must be in Ready state”. The list is Ready.

Any ideas?