pi 3b+ – Why are my GPIO pins not reading any input?

Across to models of Raspberry Pi (3b+ and 0W) I have not been able to get a single pin to read input.

• I used 3.3V and ground
• I have used the RPi.GPIO in python and also pigpiod to try to read
  the input
• I have used a multimeter to check that the input voltage
  is not the issue
• I checked every cable I used beforehand.
• I have checked most GPIO pins across the two models with these methods

The pins are able to output fine.

Are all pins on boths Pis just broken? (If so how would I check to be certain?)

If I can give you any additional info, feel free to ask.

Thank you in advance for any advice 🙂