I work in the apt industry as maintenance, currently on a new property. I had a call this weekend about no power in kitchen outlets or dining room. I found a GFCI outlet in the run, tried resetting it and couldn't. that was with breaker, also a GFCI, in the on position. I changed the GFCI outlet out and when I slipped the breaker to on, it tripped. Then I removed the GFCI outlet, crossed black on black to verify the wiring down the run. All outlets checked out as wired correctly. Any suggestions on next steps?