Hello Bianca!
That sure is a quirky little glitch.
I’d like to try to run through some preliminary checks to see if we can narrow down the root cause. First I’d like to try switching to a default WordPress theme like Twenty Thirteen and then disabling all plugins except Tribe Events plugins. Once you’ve done that, check if the “Add to Cart” button is working.
I suspect it may be the way that the theme is handling the mobile view but I want to make sure we cover all our bases first.
I look forward to hearing back from you.
Kind Regards,
Jami