Whith so many add to cart buttons on the page, it is impossible to see what may be going wrong.
To trouble shoot this, first simplify.
Create the page with 2 tabs, on each tab add a static add to cart button to take the recordset out of the equation, then test it.
If it is working with both as static add to cart buttons, create the recordset for each one and then change them to Dynamic add to cart buttons and test.
Once you have the first 2 working, add the next 2, one on each tab. and test. By adding them back one pair at a time, one on each tab, you can more easily pin point which one doesn't work for trouble shooting.
If you continue to have problems, please post a link as seeing the problem in a browser may help me see where the problem is.
