I have installed magebuzz shopping list extension. when I click on the link to add a product to a shopping list in the default theme I go to a page which looks like this (and is correct) 

![correct page](https://i.stack.imgur.com/Sw5V4.png)

but if I change the theme to a purchased theme I have this empty page:

![incorrect page](https://i.stack.imgur.com/Q3kzA.jpg)

any idea where the error could be or how I could figure out what the problem is?