OPn on an LG with ezDispense means the detergent drawer is not fully inserted or was opened during operation. It does not indicate the main door.
LG identifies that compartment in its ezDispense chart. Confirm that your appliance includes the system before applying this explanation.
Check the drawer seating
Stop the cycle in the manner described in the manual. When it is safe to handle the dispenser, look for any visible object or residue that is preventing it from reaching its position. Reinsert it normally; if you feel resistance, do not tap it or force it with tools.
If you opened it to refill during the cycle, note that moment and check when the appliance allows refilling. A drawer that is properly inserted can still appear closed on the outside and yet require a detection check if OPn returns.
This alert does not prove that a dosing pump has failed. Ed codes identify other system issues, while a low-product reminder relates to the contents of the reservoir. Keep those differences in mind when noting what appears on the display.
If OPn continues with the drawer correctly seated, request support with the model and stage; do not disassemble its internal mechanisms.