In our apartment, all three bedrooms are on the same breaker. It is a 15 Amp Arc Fault breaker with a test button.
Last night, my wife turned on our portable air conditioner in our bedroom. It tripped the circuit breaker. It's not the first time it's happened depending on how much stuff my step-daughter has turned on in her room.
I reset the breaker, but there was still no power to the rooms, even though the breaker stayed on. When I hit the test button, it did trip off. But after resetting it, there is still no power to the bedrooms (all the other power in the apartment is ok).
I figured maybe the breaker was bad, I replaced it today with the same brand and model breaker. There is still no power to the bedrooms.
What do I need to check and/or replace now?

Thanks in advance,
Soren

You are in an apartment, call the manager. Don't go into the box on your own.

You are in an apartment, call the manager. Don't go into the box on your own.

That would be nice if they would return my phone calls.

Start at the beginning. It is against most city, county or state electrical codes for an unlicensed electrician to perform work on any apartment complex's electrical system.

Now for your immediate issue. One breaker supplying 3 rooms is not all that uncommon. Your problem may be nothing more than the AC unit drawing too much current (inward surge) to get the AC's motor and compressor working for a 15 amp circuit to handle with the other loads active.

That's what I suspect. Now if this same breaker still trips without the AC, then if the apartment complex fails to listen to you, then call the fire department and ask for a Fire Marshall and tell him/her that the AFCI breaker keeps tripping.

AFCI breakers are used to prevent fires. If they continue to trip, there may be an arcing condition in the circuit.