How to configure the Gateway connection in PBI Service
In Manage Connections and Gateways, create a new connection and attach it to the Gateway.
Confirm the account performing these steps has TM1 administrator permissions.
Under Connection Type, select PowerConnect for IBM Planning Analytics.
Set Authentication Method to OAuth2.
Click Edit Credentials and enable Skip Test Connection.
Click Save to apply the configuration.
Result
After saving, semantic models can use this Gateway connection.