You are missing a lot of information that would be useful in resolving your issue. Frankly I'm not even sure where to begin given how little information I have...
The 'Buy PET' button is a submit button, this means the action it preforms is based on its parent <form> element. So not having any code or information on the <form> element and its action value it's not really possible to tell you why your button doesn't work properly.
So if you can provide more information perhaps I, or someone else, could help you with your problem. But as of right now there is a lot of useful information missing that would be needed to help you.
"Given billions of tries, could a spilled bottle of ink ever fall into the words of Shakespeare?"