Unable to read the IC Card UID
Check your power source, if you are powering the module from arduino/USB=>part or something like that, there can be not much power for the module.
Also you can try powering it 5v (not 3,3 as they should be powered by reference).

In my case I have had problems reading some types of cards, and I have solved that problems by giving better power supply, also higher power supply than in reference for some of the cards.

"By magic" the cards that were not working started working as a charm.

Also you should check if the cards you are using are all  ISO14443 A

Only that kind of cards is compatible with that reader.
So if you got type B, or other type of ISO cards, that will not be working.
Some of them may use different frequency, there is a bunch of standards around.

Also as said before the cards can be damaged, or could be corrupted if you tried reading UID while writing to the card, the problem is known , and in that case you can damage the UID.

I hope it helps you.
cheers