I'm thinking the little straw in the nozzle will allow the product to be more forcefully injected between the tight space between the stopper and the vessel.

I think I waited 2 days, tried several times to "giggle" the stopper and on about the 3rd day it was loose enough to remove the stopper. Good luck.

Something like Blaster Silicone lubricant, about five bucks and a major chain store near you. I would soak it a few times and then gently try to rotate the stopper a tiny bit right an left until it breaks free.

Not pushing the Blaster brand, there are probably dozens of liquid silicone lubricants.

I'll let the olive oil soak overnight.

Thanks for the ideas!

... might help loosen the stopper as motor vibrates - a final step to whatever else you are trying.

I tried some of the suggestions (not Kroil or Wd 40) I thought maybe if I soaked it long enough, water would seep in and loosen the stopper. So far, no luck. I'm supposed to have company this weekend, going to see if they can turn the stopper

Thanks for the idea. I'll see what kind of small appliances I have that might work.

The oil that creeps.
https://www.kroil.com/

so maybe that could help.

Stopper is still stuck. I was thinking of putting it in my booth saying there's a genie trapped in there I'll try the Windex and let you know how it goes. Thanks for the tip!