Will not start but turns over

Hi. Okay, so I have to explain how it got to this point to see if it’s messed up anywhere. The serpentine belt fell off due to the belt being messed up before I got it. Then the tensioner broke so I had to get that fixed as well. Had to put new radiator fluid in it. Then put a new belt on. Now a new battery. And now it won’t start. I can get it to turn over but it won’t fully start. I don’t know if something happened in between the times they were fixed. But I really want to know so I can fix the problem myself. If anyone can help me in some way that would be great. thank you.