dbeato
(dbeato)
3
Like @Wade0317 stated, we do not know the system that is not scanning for your machines. If you have still Windows XP machines I recommend to protect them with Anti-Virus. Since there is no more updates for Windows XP since 2014, the machines will not update unless it is the Windows Malicious Software update on the computers. Assuming that you have Spiceworks you can check the following article and threads:
https://community.spiceworks.com/help/Resolving_Unknown_Devices