DND_Reborn
The High Aldwin
The only way I could see not imposing disadvantage is if the invisible creature was also Hidden and wanted to remain Hidden.
If they aren't Hidden, the archer knows of their presence (hears them, sees dust kicking up when the moved, etc.) and would be concerned and distracted, and thus have disadvantage.
If they aren't Hidden, the archer knows of their presence (hears them, sees dust kicking up when the moved, etc.) and would be concerned and distracted, and thus have disadvantage.