Did this routing work at some point, but stopped working for some reason? My test would determine if the problem lied within the /dataset/Approval_Decision="Denied" part or in the conditional as a whole. If /dataset/Approval_Decision="Denied" works when the field is Denied, then you could try using parentheses (Condition 1) OR (Condition 2). Also try setting condition 2 to something that's always true or always false to see if it is evaluated correctly. 

You should be able to do this on a copy of the process, get the routing condition right, then bring it over to your active process. 

Worst case scenario, if you get /dataset/Approval_Decision="Denied" working by itself, you can add another outflow path for /dataset/Approval_Decision="Withdrawn", have it go to an exclusive gateway, then on to the same outflow as the denied branch. This is effectively the same thing, but doesn't rely on the OR or other syntax in the conditional.