Put him with a female this coming season and I bet he'll get the job done. Also, do you know what a sperm plug looks like? Just because you don't see what you think is a sperm plug doesn't mean he's not sexually mature. I personally believe a sperm plug is a misnomer. It's not like the snake is having wet dreams at night. What most people identify as a sperm plug is actually several shed skins from the inside surface of the hemipene. These are commonly expelled the first time the male copulates and everts a hemipene.