Please see my storymap here:
WMTS Test in Storymap
The map panel is a "classic map viewer" map with a WMTS layer of David Rumsey 1736 Moll historic map via Georeferencer. This is the URL of the WMTS:
The classic map here displays the WMTS:
WMTS Test - 1736 Moll
But the WMTS layer is missing in the same map embedded in this storymap.
Esri, could you please comment on this?