First are you getting any codes ?
The lock off is operated by the engine controller when the controller sees that engine is turning over via the rpm sensor and all safety inputs are there it sends a voltage
Through the relay - fuse box to the lock off
If no codes on dash and you are getting voltage at lock off I would start at lock off
A lot of people forget about the negative side of the equation so also check the brown wires
To insure you have a good negative