Replacing 2speed pump...only working on low

We replaced our 2speed pump with a pentair super flo 2speed pump. Our existing wires were 2 blue hot and 1 green ground. We plugged the hot in and the ground. The motor is only running on low so it will not prime the pump. On the high low switch there is a white wire at the high position and a yellow wire at the low position. There is a black wire in the middle with a plastic cap on the end...where does that wire go? Does it have to do with the switch only running on low? So confused...thought it would be plug and go. Please advise. I don't see how to attach a photo or I would

Did you get things worked out?

sorry...I never replied to your response. Yes we did get it wired. Had an electrician look at it....working great variable speed.

Thanks for the update!