This might be a one time oops or something but I was down to my last ball in AS last night. No biggie, I'll get some more when the prompt comes up. Yop, there it is, clicked on buy now and after a bit of a pause I get the "Oops, something went wrong. Go to the Pro Shop to complete this purchase." (paraphrased)
Again, no biggie, went and got them. Today I notice I have 7 balls instead of 4 so I go to my account to see who gifted me balls. Lo and behold, don't I see where I purchased them myself. LOL. Apparently that message in the game that directed me to the Pro Shop wasn't so.
Moral of the story-if you buy balls in the game using that prompt and get that message, check to see if you got them anyway. :-)