Must common issue is the mic isn't wired for the radio. Could also be a damaged mic. I would start by trouble shooting with another microphone that's known to work and is wired for that radio just to rule out the radio.
These days the adapter cords come in handy. I bought the small adapter plug instead of the cord on Amazon so I can use 4 pin mics on the 5 pin 148. The plug is also much cheaper than the cords.
