P3015 and P0A80 Codes and Combustion motor won't start

Hello ,

I have scanned my Prius C 2013 (126,000 miles) because the HV message and the combustion motor won't start. It showed the P3015 and P0A80 Codes. I hear a humming sound where the battery is located. At first I thought it was the battery fan, so I replaced it yesterday. Once replaced, the car operated Ok without the message for like 13 miles and then it came back. I have changed modules in the past for the HV Battery, but this is the first time the combustion motor won't start. Could any one advise on why this is happening?