I tried to use one on my Absol but it didn't work. Can you only not use them once your EV's are maxed out, or does it depend on something else?
Using one berry when you have over 100 EVs take it down to 100, then every one you use after will be reduced by 10. did you make sure that berry corresponds to the right stat? Has that stat not been filled yet?
When it is at the lowest stat yet. Also when you used as much stat reducing berries you can't because it will say It doesn't affect it. It is maxed out, your EVs. That is why it depends on maxed out EVs.