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Semantic Error (SEM1072): A value with the name '...' does not exist in the enumeration '...'.

In a data types worksheet or in a code worksheet, an element of a user-defined enumeration data type is tried to be accessed which is not defined in the enumeration list.

Exclude typos first.

In the data type worksheet, this can only be an initialization error.
Example:

In the code, a non-existing enumeration element shall be read or written. In the ST and FBD/LD examples below, MyEnum contains the values Red, Green, Blue OF INT.