Picked up a Lenovo T495 laptop w/ a 512GB NVME drive in it. I needed a larger drive so I acquired a WD Blue SN570 1TB unit (NIB). Before the swap I went into the BIOS and turned off the internal battery (only battery). I swapped out the drive with no issues. After re-assembly, I plugged it in to AC and the LED by the power plugged did not illuminate and the laptop will not turn on. I have done the push in "emergency" switch with a paperclip with no luck. FWIW I have been building computers since 1995 and have been using Lenovo since the IBM T42 days and am upgrading from a T440s (which I upgraded hdd/ram with no issues), with never an issue with any of my builds/upgrades until now. Any suggestions would be greatly appreciated as to why this machine will not turn on.
I personally never turn off the battery setting off in bios i just unplug the cable of the internal battery, Your motherboard is probably shorted , most likely installed the drive with its label facing down.