I just responded to a PM I received to assist a member of the community: I figured I would share it here as well to help those that never had to go through this process:
Simply click the details of the transaction and then scroll down and it will say:
"You can report a transaction problem in the Resolution Center within 45 days of this payment. Have a problem with this transaction? Click here to resolve"
Click "Click here to resolve"
Then you are going to be given 2 options. Choose "I have a problem with an item I purchased"
Then it will ask you why you are opening a dispute. Choose " haven't received my item."
When it gives you the drop down of what type of item choose "OTHER TANGIBLE GOODS"
DO NOT CHOOSE INTAGIBLE GOODS - THIS WILL CREATE A PROBLEM WITH YOUR DISPUTE
Simply explain that your items were never received. and open the dispute.
In case anyone was wondering - here is the difference between tangible and intangible goods:
Tangible goods are material assets that can be perceived by human senses while intangible goods are those goods which cannot be perceived by human senses. Examples of tangible goods are raw materials, money and jewellery while intangible goods are knowledge, information and capacities.