Not booting after replacing upper case

These units were/are notorious for GPU heat sink issues. I suspect disassembly probably stressed the board enough to fracture the well known poor solder to the GPU.

There are two known DIY possible ways to resurrect the GPU. One is the "catching fire" method. the other is Shimming under the GPU and the lower case to put pressure on the GPU.

Neither "fix" is permanent.

Sometimes this issue can be verified by applying pressure to the outside case enough to push against the logic board about where the GPU rests.

If this answer is acceptable please remember to return and mark it.