12V battery died, now hybrid system is not working

I went on a trip for a little over 3 weeks. We had some cold weather and my 2004 Toyota Prius would not start when I got back. I jumped it and got it to start but it would not start on its own. The dash lights also did not come on even when I jumped it. I replaced the 12V battery but had the red triangle of death when I turned it on after. I drove it around the block and had noticeably less power and the energy control said my consumption was around 16 mpg instead of my normal high 40s. I am assuming this is because the hybrid system isn't contributing so I am just running off the combustion engine.

My next thought is jumping it fried the DC/DC converter fuse fusible link and was going to replace that, but I am looking for any advice on what else it could be/how to troubleshoot this issue. I'm not the most knowledgeable on hybrids so links or explanations to any work you recommend me trying would be appreciated.

 

The high-voltage battery was replaced a couple years ago. This was the first time I replaced the 12V since I've owned the car.