Start with identifying the button to relay relationship;

~ identify the relay associated with the button press

~ then check the fuse for that relay, or group of relays 

~ if the fuse is good, then this next step is a great way to determine whether the issue is in the radio or the crane wiring 'after' the radio

.... pull the green terminal strip for that group of relays, and now you are looking at volt free relays, next use your meter on the Ohms setting, & probe from the common-Input terminal to these relays and probe each output for continuity, each relay when open is expected to be OL (over limit), and each relay when closed should be just the resistance of the meter wires approx (0.1 to 0.3)Ohms

-- relay(s) commanded closed but is showing Open, is bad, and the board needs to be removed & shipped in for service

-- relay(s) commanded closed, and measures a resistance greater than 0.4 Ohms is worn and needs replacement

-- Akostar can replace relays, just ship the board to Akostar after getting an RA form our site

RA link here; https://www.akostar.com/repairs

Wiring after the green terminal strip of the relay outputs is your controls wiring and we do not have knowledge of it. Wiring issues can be very frustrating, we hope the above helps you get started.