Dell G7 laptop, 2nd SSD plugged in but not showing up

Dell G7 7588, Win10 Home 8GB RAM 250 GB SSD. Went to install a 2nd drive in the open drive bay. 2nd drive Samsung 860 250 GB SSD read fine in an external drive, but when slotted into the drive bay slightly slowed down boot (from 15 seconds to 1 minute) but did not show the drive as installed, not even an error message. Clearly I'm missing a simple single step or setting somewhere- any help is appreciated.