Nope, JQuery is not needed. Also unfortunately I’m not seeing anything in our logs with this application about the payment form, so somehow the application id is just incorrect. I actually was wrong, it can’t be null or else the payment form wouldn’t load at all, so something else is wrong about it. I can only make it happen if I pass in a sandbox application id but using production (or vice-versa), or if the application id is just flat out incorrect.
In the browser console, are you seeing errors from https://pci-connect...? If so, does it say squareupsandbox or squareup?