I ran into the same issue with a small block chevy last week. The tech working on the motor adjusted the valves to the point where the truck would not fire up (71 GMC 2500). After doing a compression check and seeing 0 psi, we knew at that point after going over his work what the issue was. He said he went ‘by the book’.
So after backing the rockers off, we adjusted them in the correct sequence to zero lash, ran the vehicle, and then readjusted them once more going by ‘feel of the push rod rotation’ more than that book.
Truck ran the best it ever had after that.