Thank you for using the Syncfusion products.
Currently we don’t have the support for *.xlt to *.xltm conversion. We are requesting you to create a new direct-trac incident and Request for issue in that. And also your assemblies’ version seems to be very old. So, we strongly recommend you to upgrade your product to our latest version, which resolves major fixes and enhancements.
Direct-Trac Link: Login
You can download the latest version from the following link.
Kindly let us know if you need any clarification.