2007 Dodge Ram 1500 - Won't charge

I had the engine replaced a few month’s ago. Since then the engine sensor and after that the alternator started failing. I replaced the alternator. Still had the problem of the gauge showing not charging properly. Tried to start the truck yesterday now the engine won’t even turn over. The truck is dead, the dash doesn’t even light up but the battery is fully charged. Ever have this problem before? Help!

I would guess someone left a ground strap off.

Which engine sensor was replaced, there are a number of them?
How do you know the alternator was failing?
How do you know the battery is Ok?
What engine?

I found the problem shortly after posting. There is a red cable going from the battery and going to the outside of the fuse box and a blue cable either going to or coming from the engine somewhere. I think it might be the alarm system. It looks like it got hot at one time heated up the screw holding the two together and pulling the screw from the outside of the fuse box. when I grabbed the two cables and went to put the screw back into the hole my alarm went off and I had power. I am now today going out to repair the cable and anchor it properly. Thank you so much for your help.