Replaced front screen and now I no power

I had a bad digitizer on my iPod touch 4th generation. The touch screen did not work. I changed the screen with the digitizer and it worked for a little while. Then out of no where, the ipod went black (no power whatsoever) I opened up the iPod touch again to check all of the connections and everything seemed fine.

Has anyone ever had this problem? Everything is connected. And I also checked the battery connection and the percentage was 90% before I started working on it