According to the docs, they say the routing_email argument was deprecated in favor of explicit profile binding. This is not a bug. It is a schema enforcement update.
Locate your genesyscloud_user resource blocks.
Remove the routing_email argument entirely.
Add routing_profile_id and set it to the output of your genesyscloud_routing_profile resource.
If you are managing this via a GraphQL gateway, ensure your DataLoader batch fetches the profile ID before the user mutation. The REST API /api/v2/users/{id} now requires the profile ID in the request body for routing updates.
Running terraform plan after this change will show no diffs for existing resources if the ID matches. Stop trying to pass email strings for routing logic. It breaks the schema contract.