My Camera isn’t recognising my memory card!

so i took my memory card out of the computer and it was in there for 3 days,

so when i went to take a picture it said no card in camera! so i checked if my computer read the card and it did!

so today i got a new memory card and tried everything!

(yes i did check if it was locked and when i went to format it is said no card in camera!

please help me!!!