EDL Items are not generated when a user runs the Create Milestone From Template action in Vault.
The user does not have the Create permission on the objects shown below.
The solution is to grant the Create permission to this user on the EDL, EDL Item, EDL Item Template, and EDL Template objects.
The user also needs to have the Create permission on the Milestone Item object so that the EDL Items are linked to their associated Milestones.
Vault Documentation: Vault Help