You must Check out of your Job or Travel once you have completed Job or Travel. If not the app on the Server side gets refreshed after 24 hours and checks you out from Backend. But, you still see Stop button when you go to the Time Tracker Team app on the phone. And when you click on Stop button, you get an error message as "no recent check-ins found", so you will not be able to check out of your previous Job or Travel.
Ex: Assume that you have clicked on Start Job button and have Started Job on Monday at 10.00 a.m. and have not clicked on Stop Job once you have finished Job. When you return to work on Tuesday at 8.30 a.m. and it is still not 24 hours of Start Time of your Job, you can Click on Stop Job button to Check out of this Job.
But, if you have returned to work at 11.00 a.m. on Tuesday, you still see Stop Job button but will not be able to Check out of Job as the server has refreshed already. You see an error message as "no recent check-ins found" when you click on Stop Job button and cannot Check out of previous day Job.
In the above-said case, as you have not manually clicked on Stop Job, the Job still remains open on the server side. You should inform this to your Salesforce Admin so that they add Check out time for Job manually under Time Sheet details tab in Salesforce.
Note: As explained above if the Job is open for more than 24 hours, you cannot check out of your previous Job, but you can start new Job and work as usual.