Products not showing in the category on the frontend

[edthenet]

I have a Joomla 3.3.6 website with Virtuemart 3.0.4
I have set all products to no specific shoppergroup (and i have tried with specific shoppergroups)
I have set stocklevel but i have also set the configuration to just sell even if not in stock
The products ARE showing in the main virtuemart view (top 10, newest, specials)
When i open a category there are no products showing (sub categories are showing)

I thought maybe it was due to my templates, but when i switched to the standard protostar the problem was still there.
I have set only one vendor.

I have cleamed up the virtuemart database and installed the sample data. Now it was working. This also indicates that the template is working fine. So i have checked all the screens (categories, products, store informatie, taxes, etc.) and compared them with the sample data, but everything seems to be in the right place in the right order.

Now i don't know anymore.
Can somebody please tell me what i'm overseeing?

[edthenet]

I have also created a new category manually and in this category i created a new product manually. This is all working fine.

The existing data comes from a converted VM2 store but is not showing.

[Topknotch]

I also have the same problem.
I transferred site from a 1.19 to 3.0.6.
I had to create new categories, leaving the old ones in place ready to move.
The main categories, only 3 are set to Category Browse Page - categories, they work fine and when clicked on show the categories.
But when you click on a category it is empty althougn I have put products in it.
To test ,I have published the old categories and when you click on a specific one it shows the products, but not on the new catgories.
I have checked the settings and they are identical but just no product shows in the newly created category.
I am pretty sure I must be missing something very basic but I cannot see what it is!
any help is greatly appreciated.
Thank you.
sorry this on joomla 2.5.28