The customer says the order never came. Visa 13.1, Mastercard 4855, Amex C08 and Discover RG all turn on what your tracking shows.
Tracking shows the order delivered to the address on the order. For digital goods, your logs show the customer opened or used what they bought after paying.
There is no tracking, or the tracking stops short of delivery. Without proof the order arrived, the odds are poor, and Decide will usually say accept.

Decide checks this for you on every dispute.
It reads the dispute type, checks the evidence on file against what decides it, and weighs your odds against the amount and the fees. On a filed chargeback it says fight or accept, with the arithmetic and the due date. For the ones worth fighting, Fight drafts the letter for you to send.
Ship with signature or photo confirmation on physical goods, and log the first access on digital goods. These disputes are decided almost entirely on delivery proof.
See when a chargeback is worth fighting, or what to do first when one arrives.
Measure is free. Decide adds a recommendation on every dispute.