Transducers do go bad (or get weak) over time ...
*Try Restore Defaults ...
*Try removing the xducer, temporarily mount then ducer to a pole and stick it way down in the water (to test that nothing is blocking the beam ...
*Try another head unit on your xducer to troubleshoot your xducer ...
Call HB after all the above ... 1-800-633-1468
Rickie