Well you said the magic word, PC. So yes it is your PC. See windows has issues with SD cards with OS’s on them. In order for your card to be detected on your computer I’m guessing you’d need drivers maybe?
I do find it a little odd that it doesn’t detect it though. I have windows 10 and it detects it is there at least… Anyways doesn’t matter what Windows thinks if your Raspberry Pi boots up does it? Anyways I replied to your other post on how to get your robot running, so I’d try that before thinking your card is broken or anything like that.