Maintenance Stores Personnel reported he mistakenly advanced a hazmat parcel as a 'No hazmat on board NOTOC'. This mistake resulted in the undocumented air transport of hazmat.

Narrative

AWB (Airway Bill) XXX-XXXXXXXX was booked at cargo desk from ZZZ to ZZZ1 and on to ZZZ1 to ZZZZ. The 14-piece trek bicycle with 2 dg batteries was accepted by employee Person A. Then the piece was relocated to the DG rack in ZZZ by employee. The 14 piece with 2 DG was planned by Person B for flight Aircraft X in Cart X. The cart was then relocated to XX where the flight gate changed; and the ramp failed to relocate the freight and it was refused in the emergency response system at gate XXX. The cart was then transferred to back to ZZZ warehouse where Person C was tasked with replanning. When I replanned; it I looked in the cart compared the AWB and went to input the data. When manifesting the trip for Aircraft Y I pushed NOTOC the system read NO DG so I proceeded to plan the flight for on time departure. That flight then went to ZZZ1 were all 14 pieces was loaded into a cargo container by another employee where the undeclared DG went international to ZZZZ.Cause: When replanning a cart that the is being reused for a same destination the flight and different flight number the process is drag and drop. When a NOTOC is refused it then shows in the system as NO DG. indicating that NO DGs are on the flight.The manager showed me that there are 2 little window Icon the click on that opens new windows to show DGs. I asked why was this never covered in training for this position and she replied I will get back to you on this issue! Suggestions: Training on rebooking DG in new cargo system.