Open neutral reading
For any suspected open wire, the steps are the same:


Shut off the circuit.
Remove the outlet cover, unscrew it, and pull it out to inspect the wire connections to the outlet.  Fix anything wrong.  Push it back in and screw the outlet back in place.  I defer replacing the cover to facilitate probing in place with a voltmeter if needed.
If it is acceptable or you are not extremely confident of being able to avoid the exposed contacts, switch off the main breaker.
Open the service panel by removing the cover to inspect the wiring inside.  Test every mechanical connection by grabbing each wire near the end and wiggling firmly to verify a secure connection.  Repeat for every end in a circuit breaker, every ground wire, and every neutral wire.
If you still can't find the problem, you may have to check every outlet on the circuit between the panel and the misbehaving outlet.  If you don't know the sequence, just check all of them.  Occasionally there may be wall switch boxes which contain a junction for the circuit.