I just tested using Photoshop 21.2.6 and everything works fine, see screenshot below.
I have recorded action with single step to save as PNG in specific folder on Desktop, see details how I have created working droplet.
And by the way, droplet should copy action and all steps so you do not need that action in Actions panel. Droplet is running action, one that is copied and travels with droplet not action in your Actions panel as many people believe. Test it, do not believe me, create droplet then save just in case before deleting action from Actions panel. Drag images onto droplet to see if still works (that is how I get conclusion).