Duplicate of BUG-000093126: Fix will be available in 10.5
解决办法
1. Add this service as an item to My content in Portal for ArcGIS 10.4.1.
2. After adding this service as an item, click on the drop button next to the layer name following by choosing to add this layer to a new map. The service can then be added to the Portal for ArcGIS map viewer. However, it still cannot be added as a basemap to the Portal's map viewer.