I just tried this several times and it works for me. Please bear with me while I ask a few stupid questions.

1. How many items are you trying to stock at once? Reminder that it will only stock 250 items at a time. Stocking more will take more than one time.

2. Are you making sure that you choose where the items go? It is not an automatic stock to your shop.

3. Are you getting any error?

4. Do you have any CSS or add-ons to your browser that may be blocking the function?

I don't know what you were doing before, but you still have to choose where it stocks to. That button is just helpful if you hit the all button to shop or vault or etc., that way you don't have to scroll all the way down to complete the quickstock.

I find it useful when I am stocking all to one place. shrugs But I am going to go ahead and lock this up since it is working as intended.