fails for anon users even though auto account is working

I am using uc node access to sell access to premium content nodes on my site. I have spotted that all works well if the user is already logged in. But if an anon user buys a node acccess product. it fails. I have auto login enabled after transaction completion. So if he then buys the product (again) it works!. The transaction shows in his account transaction history but it is not granting access. Guidance please