New pump won't prime

[ButchM1]

I replaced my Hayward pump on my jaccuzi with a compatible A.O. Smith 2 hp pump. I also have a 1.5 hp pump for my pool and a 1 hp pump for my waterfall. My new pump will not prime. Could I have wired it backwards? The new pump will backwash though, so I know it runs. Thanks!

[PoolDoc]

The new pump will backwash though, so I know it runs.

I don't understand; how can you backwash, if the pump is not primed, and not pushing water?