If there is no contact with the pins or no resistance, then the card is too thin. If the card is too thick you will not be able to slide the card through the pins without bowing out or bending pins. Err on the side of caution and never force the card through.
Important: do not attempt to shove or jam the CPU in.
A toothpick or small tweezers are similar options that can work.
Always be careful when re-bending the pins a lot, as there is the risk of breakage
