240V outlet not working, reading 120V on each leg, 0V between legs
Hmmm.  Are the working and non-working outlets on different circuits? If so, it sounds like your alleged &quot;electrician&quot; put the 2 hot wires for the non-working outlet on the same phase. If so, I'd have a different qualified electrician check out his other work.
To fix this, if the non-working outlet hots are on the same phase, you need to move one to an opposite phase. In fact, if that's the case, it's a major screw-up.  Both hots on a 240 volt circuit need to be on the same double pole breaker. Lots of speculation on my part here. Pictures of the panel with the cover removed would help. I probably should have posted this as a comment, but I had too much to say!