Semantic Error: A function or method with the name '...' does not exist.

In an ST code worksheet which is part of a FB or program POU, a function or a method is called which is not available.

If a user function is called, make sure, that the called POU actually exists in the folder 'COMPONENTS | Programming > Local > Functions & Function Blocks' or any subfolder.
If a firmware function is called, make sure that the appropriate library is included in the 'Libraries' folder in the COMPONENTS area.
If a method in a called user-defined FB POU is missing, make sure that the method is available in the respective function block POU ('COMPONENTS | Programming > Local > 'Functions & Function Blocks' or any subfolder).
If a method is missing in a called firmware block, make sure that the appropriate library is included in the 'Libraries' folder of the COMPONENTS area. If the library is available, contact the library provider.