I've pretty much resolved this issue myself, but here's the problem (you may want to verify/test this at WPMU DEV) FYI...
Setting up Snapshot Pro on a website for the first time, and going to the Managed Backups page, it asks you to enter a key and gives you a link to The Hub where the key can be found.
On my Mac, I'm in the website admin area on Safari, and I click the link. It takes me to The Hub with the website loaded and the backup tab selected. I can see there's text "SNAPSHOT KEY" with a grey button next to it "VIEW KEY". But clicking this button does nothing.
I was about to post a question asking how to fix this or get the key, but then I realised it's Safari... some websites don't work or get tested much in Safari and some things don't work as expected.
So I tried the same link to The Hub in Firefox and when the page loaded, I was presented with my Snapshot key in a modal widow.
I imagine this is what's supposed to happen in Safari as well. But it doesn't seem to. You may want to look into this.
Safari 10.1 (12603.1.30.0.34)