More over I was struggling for a day on this. Then I found that because I put dd() in same request while cart add, the so session was not created for cart.
Try to first do the
Cart::add() and no
dd(). Then comment the
Cart::add() and uncomment the
Now you should see content, and a rowId. Now you should be able to delete it.
When you perform a
dd() method, it will make the script die instantly, so the session is not written.