I apologize if this is obvious and is answered somewhere else, but I wasn't able to find by searching.
SCCM 2012. I have a few thousand Windows Embedded Standard 7 (SP1) systems. I have a Software Update Group with the latest updates and I've deployed it to a collection with a test system. When I check that system it says "There are no updates available for your computer". If I run a report in SCCM it shows "Not required" for all the updates in the update group. However, if I click "Check online for updates from Windows Update" from the client it eventually comes back with a list of required updates... including those that are in the deployed software update group. I have tried changing the deadline for the deployment from 'As soon as possible' to a specific time with no change.
I did see this in UpdatesDeployment.log "no current service window available to run updates assignment with the time required = 1". This machine has several maintenance windows but none are greater than 180 minutes. I've temporarily disabled all maintenance windows for this collection and that message has disappeared from UpdatesDeployment.log, but the problem persists.
Another thing that is strange to me is that when I take an example KB and look at compliance, about 80% of my 3,000+ machines are "Not Required" but there are some that are required (unfortunately none of my labs)... these are all the same OS and built from the nearly the same image (it has changed a bit over time so I can't say 100%, but certainly none of them have the March-2016 updates installed yet).
Any nudge in useful direction would be appreciated.