We've been running a portable A/C in our studio apartment for 5+ years (coastal CA, no central air). We discovered, upon adding a toaster oven, that if we run the toaster oven while also running the A/C and microwave, the breaker would trip. We figured that out pretty quick, and were careful to run no more than two of these items simultaneously. We've maybe tripped the breaker 10 times since then, and only when forgetting the 3-item rule. 2 or 3 months ago, we replaced the A/C with a newer unit of similar specs. Everything continued working normally for another couple months. Then, maybe two weeks ago, we suddenly lost power in the two outlets connected to this breaker, but the breaker itself had not tripped. I checked the box and the breaker was still in an 'on' position, i.e. had not been tripped.
I checked some online sources (YouTube videos, mostly), and they basically suggested disconnecting everything from all outlets with the breaker off, and then turning it on and trying things again. That worked briefly a few times, but did not stick. Eventually I was able to move the A/C to a different outlet that runs off of a different breaker, and it's been fine. But the two outlets that are connected to that breaker do not work.
What this all means I don't know. I plugged an outlet tester into both of the outlets, and it's giving an "open neutral" reading. I also tested the outlets with a multi-tool and they're not getting any voltage whatsoever. Interestingly, during the course of this I discovered that the kitchen garbage disposal is also on this same breaker, and it DOES work (standard wall switch).
I'm at the point where I'm starting to feel out of my element and thought I should reach out and see if anyone has any suggestions (unfortunately, going to the landlord is not an option).