Pro Sites Checkout Page Creation Issues

I'm currently trying to set up Pro Sites on my multisite network. I just installed it and set it up, but I'm getting this error.....

"There was a problem finding the Checkout Page. It will be created when you save the settings on this page."

I save the settings, but that message just doesn't go away. Please help. I'm very new to this and am under a time crunch. I've tried following every tutorial I can find, but nothing seems to help....