Solution
If the salt grains on a client system is missing its workspace value, the asset tags associated with that client system will fail to update. Usually the systemlink_workspace field is the only one you will find in your client system's grains file, which is located at this path (no file extension):
C:\ProgramData\National Instruments\salt\conf\grains
If you don't see the systemlink_workspace field in your client system's grains file, just Refresh that client system in the SystemLink™ systems table, which will automatically cause the correct workspace value to be added to that client system's grains file: