I've added "jotform" facility through the 'power-ups' feature
I created an account on "jotform" and prepared a form to link to my trello account
Back in trello, after creating a card, I clicked on the "JotForms" button so as to fill out a form and got the 'authorize' message with the "Link your JotForm Account"
When I click on the link, I briefly get a pop-up and then it disappears
Please note that I have not disabled pop ups from my chrome browser