I am stumped...I have not had an electrical problem in my family room and have lived in this home for 11 years...until a few days ago. A few days ago I plugged a laptop charge cord (new and in normal condition) into an outlet in this circuit and it didn't work. I checked the breaker and it wasn't tripped so i flipped it OFF then back ON 2-3 times without remedy. Next, a single gang floor receptacle in that same circuit of 6 outlets, showed reverse polarity with my outlet tester. I checked it because for a long time the lamp that was plugged into this outlet has had a make/break intermittent connection at the plug/receptacle prong location with no concern for the outlet itself or it's wires being loose. I replaced the floor outlet (white to silver screw and black to copper with ground to green screw) thinking this could be shorting-out the circuit and the tester then showed all outlets in this circuit as OPEN NEUTRAL. I had not seen that previously and never had an issue with any outlets in this circuit...not even the outlet that first caught my attention with the laptop charge cord not powering on. I plugged the lamp in to this same floor outlet and it illuminated for 2 seconds then turned off. The entire circuit has not worked since the laptop charge cord failure.
Since then, I have checked ALL SIX circuit outlets, replaced all six receptacles using screw connections and not using stab connections, visibly checked all box wire connections (and all look very good). I then checked all other outlets in my home and all test 'Normal'. I even looked in my attics and crawl space. I looked for GFCI's that might have been tripped but all are normal (even turned them OFF then back ON). I turned my breaker for this circuit OFF then ON many times. I removed my panel door and made sure that this circuits black hot wire was screwed tightly to the breaker then followed this black wire to the romex panel entry location, located it's paired white neutral wire, followed that white wire to the panel bar it is screwed into and made sure it's connection is tight (both were affixed appropriately). I even checked and tightened ALL other wire screws on both panel bars. I was stumped...I even reversed the black and white wires in the floor outlet i installed just in case the manufacturer, Hubbell, made an error in assembly with the copper and silver screw locations. Of course, that showed reverse polarity so i returned that single gang receptacle to it's original and intended configuration (white on silver and black on copper).
End result, my family room circuit tests OPEN NEUTRAL despite my doing everything I know to do. This is a first floor room with a vaulted ceiling and no electrical outlets in this circuit outside of this one room (I tested). My crawl space, below, is clean and dry with no visible signs of wire damage. My panel screws are tight. My outlets have been replaced with new ones and screw connections were made tightly.
I also tried two different three prong testers with the same results. After reading some comments, i checked my attic where there is an attic vent fan that i know has been in disrepair for years...but it is on a different circuit and unrelated (when i turned off the family room circuit in question then tested the attic fan romex for current it is still hot)...so i assume this wouldn't relate to the open neutral family room circuit issue.
I am at a complete loss and would really appreciate any help.