Put the battery on charge,see what the voltage is.
Remove the fuel filter and inspect.
Check all your connections on the fuel line,you might find it weaping somewhere.
If that all checks out,join a clear bit of hose from the supply side of your filter to the fuel line itself.Providing you have refilled the fuel filter housing the chipper should fire and pull diesel up past the clear bit of hose.It might need to be bled at an injector or it might not.
Now you know you have diesel from the tank to the filter and from the filter to the pump.leave it and see if air appears in the clear hose up at the filter housing. Providing the housing is at the highest part of the fuel line.Thats all if you just dont want to replace the fuel line which you might end up doing.There is a slight,slight chance there is something floating around in the tank that blocks the end of the fuel intake but thats an outside chance imho.
Kubotor engines did have pretty weak lift pumps,I have replaced a couple with electric lift pumps but the symptoms were the engine farted and hunted rather than were hard to start.