@zong is actually correct. 99% of the time this is an autofac related issue.
I am sure you have gone over code numerous times but somewhere one of your dependencies in one of your services is not being 'picked up' by autofac. The only other thing I have run across is if your controller is not inheriting BasNopController.cs OR you are inheriting BaseNopController.cs AND you have a parameter less constructor. BaseNopController.cs already has a parameter-less constructor.