When viewing a web map with a map service in 'Operations Dashboard for ArcGIS', that has symbology set according to Unique Values category in ArcMap, all the points draw with the symbology of all other values. The same map service if viewed in ArcGIS Online webmap or ArcGIS Desktop renders with correct symobolgy.
Here are the steps I followed:-
1. Create an ArcMap document with points rendered with Unique Values category.
2. Publish an ArcGIS Server map service.
3. In arcgis online, create a webmap with that service.
-The service will render with correct symbology in the webmap. (see image below)
4. Add this webmap to Operations Dashboard.
-In dashboard the features will display with 'all other values' symbology. (see image below)
ArcGIS Desktop and ArcGIS Server are at version 10.4.1 on Windows 10.
If the a sample service from Esri is used to create a web map and view in Operations Dashboard, the problem is not reproducible. The below sample service was used.