The HLI issues this message if an assembly instruction is not available. Note that the assembly instruction is still known and may be available for other operands.
This error message is relatively unspecific. It shows up if the type of operands does not match (e.g., a register instead of an immediate) or the number of operands is different, or the overall operand syntax is wrong. If the error is not obvious, we suggest that you find the error by comparison with a corresponding instruction, but with plain assembly operands.