If you have different versions of AutoCAD in your office, you might have this problem. AutoCAD 2013 has changed the file version (we all already know it), it means lower versions can’t open it.
The same thing happens if updated your template file with AutoCAD 2013. You open your template file, modify it then save it.
If you share the templates with your coworkers, they who use AutoCAD 2012 or older will not be able to use it.
AutoCAD does allow you to save to older version. However, it only have versions for DWG but only one DWT. It means you can’t save it to lower DWT version, and your coworker can’t open it using AutoCAD 2012.
So how you can save to AutoCAD DWT 2010?
DWT is actually DWG file. Autodesk just use different file extension to differentiate a drawing and a template.
You can save the template as AutoCAD 2010 drawing. Then you can change the extension in Windows Explorer from DWG to DWT.