I am trying to book a KLM flight from BER to SLC this summer, and I have unused Delta eCredits that I would like to use for the flight.

Here are the details of the flight I am trying to book:

BER to SLC June 22nd, 2022 6:00am to 8:15pm
BER to AMS (KL1818), AMS to LAS (KL0635), and LAS to SLC (KL7641)

SLC to BER July 22nd, 2022 9:00pm to 4:40pm +1 day
SLC to AMS (KL0610), AMS to BER (KL1829)

When I price this flight on google flights, I am quoted €523 if I book directly through KLM. I am not given an option to book through Delta. If I go to Delta's website and try to book the same flights, this particular itinerary does not show up.

I thought I would try to work around this problem but searching through ITA Matrix and using powertools to maybe be able to book through Delta. However, when I searched the flights, I did not even find the itinerary from google flights as on option on ITA Matrix. Routing through Las Vegas was not an option, even if I tried to book through KLM.

Am I doing something wrong, or is there just a difference between ITA Matrix and Google Flights?

Thanks for any advice or ideas that you all may have.