Description: In a Multiplayer match I attempted to strike the dwarf wizard with my warrior melee attack (Strong Bludgeon). However the error message "There are no valid Targets" appeared and prevented me from doing so. The following turn when the Water tiles expired I was able to strike the dwarf. The turn previously I was able to strike the dwarf with another melee attack card (Sundering Strike) Expectation: I expected to be able to strike the dwarf wizard (circled) with my warriors melee attack (Strong Bludgeon). Attached is a screenshot of the round. - Keys
I can't tell for sure, but it looks like you might have Squeamish on your warrior. This would prevent you from targeting any character with an attack that has a higher damage than their health.
Would be nice if some sort of reminder popped up when Squeamish is preventing an attack, because it's easy to forget about if you're in the habit of rapidly clicking through your Traits.