DotNet domain dashboard shows "Err" missing icons.
DN-344 is the bug ID for the missing folder/icons.
"system:core_mb.46 not found" in Management Server logs
We verified that there was a bug in 5.6.6, the cartridge used to make use of this wcf component (system:core_mb.46) which has been removed in 5.6.2. Fixed in 5.6.7
Upgrade to 5.6.7 .NET Cartridge.