NVidia GPU is not being detected

Hi, I have an old Inspiron 14R 5421 with GeForce GT 730M. Since it was running hot from sometime, around 85-90+ degree C while playing games (the CPU), I took it to a local service shop to get it cleaned up & have new thermal paste applied. The GPU was working fine and the CPU was running around 75 degrees. I once opened it personally to clean the insides a bit more but didn't touch the CPU/GPU side. But 2 days later, I realized that the GPU is not visible anywhere anymore, like in the right-click options.

When I open NVidia Control Panel, it says, 'An NVIDIA graphics card was not detected in your system'. I tried installing the driver from both NVidia & Dell's site but they both say - 'This graphics driver could not find compatible graphics hardware'. I was able to see the GPU under display adapters but only after enabling 'Show hidden devices'. To clean install its driver, I uninstalled it but it's not visible anymore in the list. I re-opened the laptop to check if I missed something but AFAIK, these are all soldered on the board.

Is there some way to check if this a software issue or a hardware issue? Any solution to this problem?

Thanks.