Recently I did a Windows 10 deployment with a new task sequence and deployment. Before running I updated my boot images first. This is described in the following blogpost: Update ConfigMgr 2012 R2 SP1 with Windows 10 boot images. During PXE boot however no task sequence became available and the system was restarted. When looking in smsts.log (press F8, start CMtrace, and open smsts.log in X:\Windows\Temp\Smstslog) the following message was seen: Skipping Task Sequence because it is not active yet & There are no task sequences available to this computer.
Trick is, you need to change deployment scheduling on the task sequence (or other deployment). In my case I changed date/time in "Schedule when this deployment will become available" one day earlier. For it seems the time(zone) used by ConfigMgr is not the same as used on systems during deployment? After changing deployment scheduling everything was working fine again!
Having a look at smsts.log again the following message is seen now: Found mandatory deployment & Using mandatory deployment. Happy that Windows 10 deployment can continue now! :)