Assuming that you are running compatible hardware on both sides, the most common cause for this issue is your local subnet configuration. You’ll have to first verify that your SmartThings hub is able to communicate with your Powerview Hub directly over your local network. Even though both your ST hub and PV hub may get to the internet just fine, talking to each other requires that your internet router/gateway/switch permits it. Some routers isolate wifi from wired connections, others apply more granular restrictions. There are too many possibilities to enumerate here.
If you have confirmed that these two components can properly communicate locally, then you can verify that the PV hub is accepting normal HTTP calls via your browser. If it doesn’t, then there’s something wrong with your PV hub. Beyond that, I don’t have any ideas to offer.