dell latitude 7400 dead after thermal paste replacement

[Jonjojonz]

hi sir, bro, i have problem my dell 7400 dead after replace thermalpaste, just blink yellow led/charging light when pwr button press n no taking current anymore, its hard to remove heatsing, just gently lift up then i put some solvent/thinner try again n wiggle it n can remove heatsing, thermal paste dry, when done assembly its dead, i do unplug battery first of course, whats wrong please help sir