Diagnosing a dead MacBook Pro
I had the same issue when upgrading my RAM.
It turned out that the SO-DIMMs were not properly inserted.  

Try the following: 


take out both SO-DIMMs
re-insert the first one and make sure it goes fully into the lower socket
try rebooting

if it works, shut down again and insert the second SO-DIMM (again taking care to fully insert it into the upper socket.)



Good luck.