In ArcGIS Enterprise, the style of a vector tile basemap (for Export) cannot be changed by uploading a JavaScript object notation (JSON) downloaded from a second vector tile basemap (for Export).

Workaround

1. In ArcGIS Online, save the desired Style in the item details page.
   1. Log into ArcGIS Online.
   2. In the item details page, click Edit in Vector Tile Style Editor. Download current style and it will download a .json file.
2. Go to ArcGIS Enterprise, open the added basemap in Map Viewer Classic. Click on Change Style and tweak the default style.
   1. In this case, change the color of Land/Ice by clicking Outline Color and choose any color before clicking Save Style and Close.
3. It will show the saving style process, and after it is done, an error message, "Error: The layer, xxx, cannot be added to the map" is returned. Click OK.
4. Open the item details page of the basemap. Click Update and choose the .json file saved in step 1. Update the Style file and it will successfully update.

Steps to Reproduce