When the PC clicks the locked door, the OnFailedToOpen script would fire.
The OFO script makes the PC start a conversation with the door.
Since the door has no own onConversation event, the default nw_g0_conversat will fire, which in turn calls BeginConversation()
The conversation assigned to the door will start.
This worked fine in v1.69.8109, but does not work anymore in v74.8172 (and probably version before). Apparently nw_g0_conversat is no longer fired for doors (and I assume placeables too), so the dialog will never start.
If you change the direction of the conversation, so that the Door starts the conversation with the PC, the dialog launches as expected.