It’s a 2015 ram fully deleted with mm3. Back in December I went to drive it after sitting for a few weeks and the battery’s were dead so I jumped it off my wrangler and started no problem and drove it for the weekend with no issues. I put a tender on it the next weekend for the winter. I went out last weekend to start it and there was nothing happening. Key still unlocks the doors and interior lights come on but when I put the key in the only thing that happens is the dash gets brighter. When I turn the key nothing happens. No more lights no dinging no radio like I’m not even key. Though maybe the batteries where toast so I put new ones in, no change. Checked all fuses I could think of and couldn’t find any bad ones. Tried the spare key and no change either. Unhooked batteries for the night to see if something, anything would reset, no change. I called the shop I use and he’s afraid I cooked the ECU when I jumped it. I’ve been searching the internet the past couple of day but couldn’t find much with this particular problem. And if it is the ECU, what would be he next step? Thanks in advance.