I had the same issue. Having a 0 on the gauge prevents the forks from lifting but driving is ok. No codes. The battery is fully charged. for some reason, the circuit board stops reading the battery voltage. I replaced the circuit board in the arm and this fixed the problem. The part number is: TO 00590-47051-71

If this is a 24v truck which i'm assuming it is.....
24.7v after an all night charge is not a good sign.
After charging a 24v system should be reading around 26 to 28v.
Do a load test on each battery if it has a battery pack with multiple batteries or if it has a single industrial battery use the hydraulics and load the system to see what kind of a load drop you have.
If testing single battery it shouldn't drop more than 1 to 1.5v, if the industrial type and it drops more than 4 or 5 volts under a full load in a 15 to 20 second loaded stall then you need new batteries.
Also plug the charger in and use a VOM and verify it is charging.

The unit has a % charges display on the digital handle display. I am not sure if it is resetting it was operating normally about 6months ago

Does the unit have a battery monitor.is it resetting. is it plugged in?