Siemens alarm 12550: Channel %1 block %2 name %3 not defined or option not installed

What it means

An identifier used in the program is unknown: it was never declared with DEF/PROC, is not a built-in variable, or accessing it requires an option that is not enabled. Check spelling, add the declaration, or verify the corresponding option/compile cycle is installed.

Likely causes

• Variable used before its DEF declaration
• Misspelled variable or subroutine name
• Access to system variables gated by an unset option