I would guess that you hydraulic EEPROM has "lost" its settings. I would suggest you carry out a factory reset (do this twice) which may cure the problem, after which you will need to change any parameters you have set out of the standard settings. If this does not cure the fault you may need a new logic card.
The description of the fault is below.
(1) Situation
Indication: "67" display. All vehicle operations inhibited. Line contactor OPEN.
(2) Possible cause
Faulty EEPROM on hydraulic logic board.
(4) Checks
Set Setup Option Group 3 data, then set Setup Option Group 1 and 2 data (default data).
If necessary, adjust Setup Option Group 1 and 2 data again.
See pages 2-111 to 2-114. (Procedure of "Setting Setup Option Group 3", "Setting Setup Option Group 1 and 2 default
data" and "Adjusting Setup Option Group 1 and 2")
"67" display remains Normal vehicle operation
(3) How the error code is triggered
When the logic software starts, first it reads the Setup Option data and check sum data from EEPROM. Software
compares both data. When there is difference, error 67 occurs.
(5) Replace hydraulic logic board. See page 1-30. (6) Vehicle operates normally.
The truck is 80volt with normal hyd levers and line contactor not energising
Is the truck AC or DC and does it have finger tip hydraulic controls?