First of all, give the timer a good cleaning. Carb cleaner, break cleaner, silicone spray, gasoline if you don’t have anything else (using some good judgment). Then holding the lifter out of the way, insert the notched shaft from the bottom. If it stops at the timer bushing, the timer bushing it out of alignment. You will need to remove it (timer bushing) and get it position correctly. If it is not out of alignment, all it needs is a good cleaning, and oiling.
A "Boathouse Repair" is one thats done without having tools or the skills to do it properly.