I have the 824 techmaster replacement parts manual, which unfortunately doesn't label the function of the various solenoids. Can you unplug various solenoid control coils until you identify the one controlling table feed (or do it by process of elimination)?
I'll agree, these grinders are shockingly complicated for what they do. I have an 818 Techmaster and some oaf removed the entire crossfeed stop assembly, so now it only feeds the wheel towards the operator, backfeed must be done manually.
If you are able to feed the table with the main handle while the grinder is in "feed" mode, that seems consistent with a stuck solenoid spool that's not allowing pressure to build in the main cylinder. When the table cylinder is hydraulically controlled, it also disengages a clutch between the table feed handle and the table drive pinion so the handle freewheels. Same for crossfeed.
Please let me know if you find a manual, I could certainly use one too.