When attempting to copy Tasks from Template nothing is being copied over. The error below gets generated in the app-ca.log file.
ERROR 2020-11-19 14:16:47,312 [http-nio-8082-exec-107] view.ViewL10nSAXHandler (session:odf.filterStateChange) Could not locate vxsl file '' in component odf
Release : 15.8.1
Component : CA PPM APPLICATION
The issue was caused by one of the existing tasks in the Project that were trying to copy tasks into.
The Task may have been corrupted in the target Project.
After deleting tasks, 'Copy Tasks From Template' worked as expected.
If you can copy the tasks one time but not a second time this is because the TaskIDs are populated on the template and auto-numbering is turned on.
With these features you cannot copy the tasks more than one time as the TaskIDs will try to be copied again to the target project.