F150 with new:

Head gasket Valves Timing kit Cht sensor

Code p1299 is showing as permanent, and the truck will not start. If hit with ether is starts right away and runs fine. No over heat. No other codes. Has been driven for hours on highway and city. No issues. After driving, shut off and immediately tried to restart, same problem. Cranks, no start. Shot some ether, started right up and ran fine again. Still no other codes. What am I missing? Any help is appreciated.