By the numbers.............1)
Go here: http://www.radiomanual.eu/ICOM.html2)
Scroll down until you see the Icom IC-718 service manual. Download same.3)
Adobe Acrobat may ask you if you want to install a JP font set. Your choice, but probably a good idea.4)
Scroll down to Section 12 and notice illustration 12-1 in the upper left corner. This is the filter board that carries the T/R relay plus six bandpass filters.
Each filter has a relay on the input and another relay on the output. That's how the filters are switched in and out of the TX line.5)
If one of those relays hangs or fails to switch the radio will not return to the normal RX passthru condition.
Translation: No RX on that band or (possibly) any band above it as the filters may cascade.6)
Go back a few pages in the service manual until you see Section 10, the block diagram. Note the bandpass filter in the upper right corner.
Notice how the last two bandpass filters are labeled 15 - 22 MHz and 22 - 30 MHz. If you flip the RX into general coverage and discover it pukes
at exactly 15 MHz, that's your clue-by-four the radio has a bad relay. Might want to tune above 22 MHz just to see if the RX comes back.
I think I've read that some of the newer radios have a relay cleaning utility buried in the menus. Check the user guide to see if this applies to the IC-718.
If not, consider farming the repair job out to a pro unless you are exceptionally talented with a soldering iron and are in good practice with same.............