Upon arrival I spoke with the customer of an issue, where half of one of the rooms that had been remodeled at some point was out. After the customer agreed to the diagnostic, I proceeded with troubleshooting and trying to find where the fault in the line is. I tested one of the breakers that was showed trip on the indicator, but was in the on position. I tested in the breaker was fine. After further testing, I found that a different breaker Supplied power to most of this room. After searching, I was able to find a GFCI receptacle located underneath of the counters to the right of the sink. After resetting the GFI I found that all power was returned. I gave the customer an option to replace the GFCI receptacle with a standard receptacle and dual function protect the circuit with arc fault and ground fall. The customer agreed and I started the work. I installed the art fault breaker and after testing, found it to trip immediately. I continued testing by switching it to just a GFCI and it