I'm going to guess that the account the provisioning is running under does not have access to that directory. The best option for this situation is typically mapping a drive to the share.
Map a drive to the UNC share.
Copy the file using the drive mapping.
Map drive (direct)
Map drive (preferred servers)
Copy file (same regardless of drive mapping technique)
Thank you DLudwig! I didn't think to try it that way. The user account I was using is a Domain Admin, and a locla admin on the CORE, so it has the rights. But, mapping a share first then copying worked great, thank you!