What is this "simple tester"? If you are using a proximity (induction) tester and are getting a "hot" reading, then I would suspect a loose neutral wire. Look at the closest receptacle on that circuit that is still working. You may have a loose white wire, probably loose because the push-in connection was used. Repair using the screw terminals.

That did the trick. The white wires at the good outlet had loosened under the cap and were not in good contact.

I never thought to go back to where the circuit was good.

Thanks