This warning message flags up when the gateway detects the rule target containing non-identifying predicates (e.g. a common case is cell value in the XPath).
Non-identifying predicates are expressions that cannot be evaluated using the gateway setup. They need runtime information in order to be evaluated. Please refer to the Gateway documentation and look for the section named Non-identifying predicates for details.
If the warning message appears, please revise the gateway rule using operators (e.g. =, >, like) and functions (e.g. regMatch) inside the rule block for the checking.
Below is an example for regMatch() function which use regular expressions to match the cell value with multiple strings.
if regMatch(value, "^LON|^PAR") then
PS. The validation has been made stricter after gateway versions GA3.1.1 (GWX-2546), GA3.1.2 (GWX-2597) and later. Prior to these versions, while the gateway may not report these as warning during validation or saving, actually the gateway was unable to handle these XPaths.