Small block starter and flexplate issue

What year trans and what year crankshaft?
If you use an early torque converter "small snout" in later yr "large register" crankshaft ...any misalignment of the starter and the larger register can allow some **** eyed movement of convertor against the pump.

Aside from that...1st loosen started bolt just a hair and try to get the solenoid gear to extend and mesh without starter motor engagement , then snug the bolts and try it.
Looking at the pics, get it wired up too. Lol