When you open a project in STEP 7 V5.7, why do you get the err | Siemens

When you open a project in STEP 7 V5.7, why do you get the error message 3280:709 "Project or library are on a write-protected medium or are protected by a rights assignment"?

FAQ ∙ Updated
Change to the more recent procedure "Always assign CPU-oriented unique message numbers" in your project or install the option package S7-PM if you still have to use the "project-wide message number procedure" in your project.