Adding a Web Map Tile Service (WMTS) as an item to an ArcGIS Enterprise portal and then using the 'Use as Basemap' option to add it to the map returns an error message.

Workaround

• Select the WMTS as the basemap through the ArcGIS Online Map Viewer Classic.
• Add the WMTS to the map using the 'Add to map' option and select 'Move to basemap' from the 'Options' menu of the layer.
• Add the WMTS as a basemap using the 'Add from URL' option and the activated 'Use as Basemap' toggle button.

Steps to Reproduce