Only feature layers, web feature layers, vector tile packages (.vtpk files), raster files, and tile packages (.tpk files) are supported when sharing a mobile map package. ArcGIS Desktop annotation layers are not supported. Upgrade to ArcGIS AllSource annotation layers to include them in a mobile map package.
Solution
Remove the layer from the map.
More information
For more information, see Share a mobile map package and Analyze your GIS resource.