Phone won't turn on after display assembly replacement

I'd like to start off by saying that I spend my summers as a summer intern at a highschool doing repairs on old white macbooks and 2013 macbook airs. I began replacing phone screens at the start of this past summer and had not experienced an issue up until now.

My sister had her iPhone 6s with a cracked LCD and through verizon and the upgrading process, it was cheaper for her at the time to upgrade to a new phone rather than repair the screen. Naturally, I saw the opportunity to fix the phone and have it around as a spare so she gave it to me. I replaced the display assembly (LCD/Digitizer) with a part ordered through ifixit.

I conducted the repair flawlessly, taking all of the precautions to avoid ESD and doing any damage to the board per usual with a replacement. However, now with the replaced screen the phone won't visibly start up and when connected to itunes it isn't recognized.

Ultimately my questions are as follows:

Was the screen dead on arrival?

Should I try and see if I can get a replacement screen if it was dead on arrival?

I should mention that I did the repair a few weeks ago at home and since have returned to college and did not bring the original screen with me (stupid), and also did not try the original screen after the initial repair did not succeed (stupider). I will try to get the screen when I can, but this is my situation. Any help and recommendations are greatly appreciated, thank you!