Chosen Solution
I replace the screen and now it won’t power up or turn on. Find My Phone says it is offline. The top by the camera feels warm.
You may simply have a defective replacement screen. I would try to re-install the original (presumably cracked) screen to see if the phone works normally. You can also try disconnecting the FCAM assembly to see if that causes the problem. Ultimately, you may have caused some issues on the logic board, as Daniel suggests. Let us know what you find.
Have you tried a hard reboot? you can do that by holding sleep and the home button for about 10 seconds.
It’s likely something major has been damaged. Could be the battery or a key component (e.g. CPU, display), but I would say the phone will either be expensive or impossible to repair.
