Boot to Blank Screen

can anyone provide any assistance?!?!

I have used this guide a few times now to successfully replace screens however I have an early 2011 17" MBP that now boots to a white screen and that is it, cannot boot in recovery or safe mode. It even turns off a few seconds after starting up. Any thoughts on what could be causing this issue?

I have double-checked all connections and cannot see what the issue could be, I did also upgrade RAM as there was one empty slot as well as put in a new hard drive. I have done this type of upgrade before but have never run into this issue. Any advice would be greatly appreciated.

Thank you!