ISSUE SOLVED
I had same issue and replace the SMD capacitor (marked red). You can see on pictures. I replaced the capcity with a regular one. The smd capacitor is placed at the pcb where a lot of heat is during monitor is on. So I replaced with a regular one which can 105°C (marked green)

This cap is responsible for g-sync. The g-sync ad-on board is also responsible for standby voltage and standby control. if your monitor is dead (no standby), replace this cap....