Try pulling the link from "my account". Use copy link location it works for us every time. Another alternative is pulling up the hub and copying the link from the browser. You can also do this from the account page. Just click the hub you want to pull up and it takes you right there.
From the word press side there is a hyperlink button in the editor. Turn the word you want to link to blue then hit the hyperlink button. It will pull up a box where you insert the link. Make sure you don't use any words in the title of the hub to link to because it is now considered spam according the the Penguin update.