can you tell us how you have solved that problem please?:)
Hi, I did complete the quest to begin with, i.e. both plusle & minun were both properly interacted whilst they are near the golden rods. Then when I went back and talked to Wattson he just kept mentioning the quest I just completed (plusle & minun). At this point, I just logged out for 2 hours next to Wattson and when I came back he decided it is time to move on :) Maybe time is all you need.