I only recently registered on the site and has to say the signup was effortless. (Apart from the email code that was send to my Spam folder, so it took me a few minutes to realize that, but that was something on my side and not a problem with the site)
I do not know if there are any known problems with Firefox browser compatibility, but the whole screen started to flash when I used the Firefox browser. (What browser do you recommend for the site?)
Other than that it was a flawless experience, so well done on that.

If I recall it correctly, Jack have ever said that firefox is the most recommended browser. He did even say that he is not satisfied with the site's performance on Chrome browser.
I myself always use Chrome browser to play at Jacksclub, I have no significant issues since I started to play here months ago.
So you can use Chrome and let him know your experience while using Chrome vs Firefox.