New SSD not recognized after installation on MB Air 13 inch 2015 model

Try an SMC reset followed immediately by a PRAM reset (hold the PRAM reset for at least three chimes so it activates several times). Maybe even try reversing the order of the two resets. Years ago OWC tech support suggested this to me when their SSD wouldn't work correctly in an original MBAir.

Are you replacing the SSD because the original one failed? Maybe the original SSD is good and the Logic Board has the failure.

Resetting NVRAM could solve the issue.

https://support.apple.com/en-us/HT204063

Could be physical - the first time I installed a blade SSD in a PC notebook I thought it was seated properly but I was wrong. Opened the computer up again, took it out and put it back in. This time I felt it snap into place.

Which SSD?