'Add Media' not working on product pages. Neither 'Slide In'

Hi

We use SimpleMarket and MarketPress to build our site http://www.firesafetysigns.me.uk

First, we used Gridmarket but as we wanted a list view for products switched back to SimpleMarket.

We have a few problems:
- Can not add image to product page via Add Media. It works on pages, posts but not product pages. We added the image as featured image but we think we should be able to use Add Media tab
- We installed 'Slide in' and worked ok when using Gridmarket but now doesn't work. We create a page within Slide In but 'View page' returns a 'not found'. We would like this working.

Look forward to your help

Thank you