From my experience something has changed. Either a permission on a folder or a path to the image or if you used variables in your template you made a change to one of them.
If this is not a new computer to the network then add a sytem migration to the first thing in template.Add a reboot action then choose Boot to managed WinPE(virtual Boot). Save the template and right click on it and schedule. In the scheduled tasks drag you computer to it and see if it runs.
That will tell you if the template is good.