I’ve been trying to get a WMS layer to show on my Omeka S maps to no avail. The Layer I’m trying to pull in is here: https://www.arcgis.com/home/webmap/viewer.html?useExisting=1&layers=628578697fb24d8ea4c32fa0c5ae1843.
I’m including a screenshot of the configuration I’m trying to do in Omeka S.
There doesn’t appear to be a WMS overlay in the link you provided. I only see a “COVID-19 Cases US” feature layer. The Mapping module does not recognize or render feature layers of this kind.