Hi
Have you checked all the connections are seated correctly?
this seems quite strange if you haven't damaged anything, try reseating the screen connectors and keyboard connectors
if that doesn't work inspect the connectors on the board and parts for damage(burned pins, torn cable ,caught under screws ...)
if you can't find any damage try cleaning the connectors both part and board with isopropyl alcohol and tips/cotton buds
if the above dent work let me know any we can have a more in-depth look at things
Hopefully this helps
Thanks:-)