An article you submit for translation should create a Translation Request record, which is associated with your action and "marks" the request in the SF data model. Sending an article for translation merely consists of assigning it; the logic lies in a apex job that runs periodically and checks for pending tasks. A translation is therefore not expected to generate immediately.

Still, if after an hour you still don't see any translation requests associated with your request, it is time to check for possible issue. Below is a list of possible causes for the flow not to be starting.

Unauthorized API connection

If your connection to the Unbabel backend is failing, this error will occur silently. To confirm the status of the connection, test it in the Unbabel - Configuration menu as explained here. If the test is failing, you will need to redo the API connection.

No scheduled translation batch job

In order for the apex job to run, a period must be set in the queue settings under the Unbabel KB Configuration menu. If the schedule is set to None, the integration is effectively halted. You can see here how to set a periodic batch job.

Wrong article assignment

There is a chance that when requesting the translation, you assigned it to a wrong queue or user. This is easily fixable. Head to your Knowledge tab, select the article translation draft and reassign it to the Unbabel queue. Then, wait for the periodic apex job to pick it up.