Error (Safety Specific Code Generator): Unknown POU '...'.

A safety-related FB POU is called in the project which does not exist. Possibly, there is a typing error in the instance name, or the library containing the FB has not been added to the project.

Possible remedies:

Insert and edit the missing FB POU.
Correct the spelling of the FB POU name.
Insert the library containing this FB POU.

If the error remains after trying these remedies and compiling the project again, contact the technical support of Phoenix Contact.