When a Translation task is created, it will be put into a task queue. A queued task will normally start running within a couple of minutes.
The main reason why a task would be queued longer than normal is that another task is already running on your store. TMS can only run one task at any given time, so any tasks created while another is already running will be queued and processed one at a time based on their creation time.
You can check to see if this is the case by looking at the tasks on the View Tasks page in our app. If you do not see a task running on the first page, you can try using the "running and reverting" filter shown below to see if there is a task currently running on your store.
If your tasks are all queued and there is no running task, or if you notice your task being queued for a long period of time (6 hours or more), please feel free to reach out to us so that we can look into the issue for you!