Why does template PDF with dummy 3D or placeholder fail to load?

Why does template PDF with dummy 3D or placeholder fail to load?

The most common issue is that the Template PDF fails to load because it has some security setting. When you open it does Adobe Reader show “(SECURED)” in the title bar? If so, please remove it (via menu: Edit | Protection | Security Properties) or re-generate the PDF with security disabled, then it should load OK.