The board usually only fits one way. Check your specific radio manual’s diagram to ensure the notch or pin 1 is aligned correctly.
Most Icom radios compatible with the UI-7 (like the IC-725, IC-726, or IC-728) feature a two-part shell. icom ui7 am fm unit install
Ensure the board is fully seated. A single loose pin will prevent the microprocessor from detecting the unit. The board usually only fits one way