Wondering what, if anything, I'm doing wrong. I can't get Delta to show me flight options if I look for 2 one way itineraries. Attempts to get a multi-city results in error "no results were found for your search. Some of our flights only operate seasonally or on select days of the week. Try using the nearby airport search or flexible date option. #ROF4002_404SM" every time, including if I change the dates +/-2 days.

AMS-SEA Nov 15
SEA-LHR Nov 23

Google Flights can get me an itinerary with either VS on the 23rd, or DL on the 24th. I'm trying to check for GUC availability etc..