S2418HN, power adapter replacement issues

Hi All,

Awhile ago we bought a Dell S2418HN monitor for our business (from a Best Buy store - in the US) . A few months ago, someone stole the power adapter. Why they would take the power adapter and leave the monitor is beyond me.

In the time since, we have tried at least 5 replacement adapters. The user guide indicates that the replacement part number is either: Delta DA65NM111-00, or Chicony HA65NS5-00 (we have tried both). All attempted adapters are 65W, 19.5V, 3.34 Amp, with a 7.4mm plug. However, in every case, upon power-on (no computer connected) - a message displays: 

"please use the adapter that was provided with this monitor"

• I've tried entering the service tag - but the Dell website finds no match.
• I cannot get to the OSD to perform a factory reset.
• I've tried pressing, long pressing, and holding each button at power-up, also every combination of buttons (15 of them).

Is there something I am missing? Or something else I should try?

Any help is appreciated.

Cory