Hello. I am a novice in the field and had purchased a used, but new FIELDPIECE LT17A. It can read the Voltage (AC/DC), Resistance/Continuity, Temp., etc, but it does not read AMPS nor AC current when using the clamp. I tried to use the clamp with my leads to read the amp on a unit for lab work, but it read 0 while my friend's Klein read 23A on a fan of a 220V unit. I also tried using the clamp to read the AC current of my lamp cord and it read 0. Previously, it was working, but now it doesn't so what gives? Can anyone help guide me to fixing this or what test route to take?? Thank you!!

Update: I tried to test the resistance of the clamp and it fluxuates in readings from 124 to 127 @ 200 range ohm setting. At times it would do that then read OL and then when testing again it would read 124 to 127??? Could the clamp be defective or the meter itself needs to be serviced??