I'm using ArcMap 10.4.1, and have created the mosaic dataset, which shows up in the TOC as expected.
When I run the Add Rasters to Mosaic dataset tool, it stops after a few seconds with the error message "No mosaic dataset item selected." (screen shot attached).
I have lidar DEM tiles (1-m resolution) from a state website that were downloaded as .img files. I've converted them to tiff and esri grid files, but the tool doesn't work with those either.
Do the raster files need to be in a different format?
Is there something preventing the mosaic dataset from being recognized?