Hi,
Has anybody came across the issue when they add products in the cart and select "continue shopping" and nothing shows in the cart.
Then when you add another product and select show cart, you can see the previous items.
Its weird.
It is probably a Javascript issue
Try to disable Joomla page cache, if you use a CDN disable cache for html,php and json(and same for .htaccess)
1. Which version of VirtueMart are you using?
2. Are you using SSL for the whole site?
3. Have you enabled SSL in VirtueMart Configuration?