How do you make a buttonhole with a Bernina 830?

Basically it is a matter of a stuck part. Flip open the top by prying up on the front or ends of the lid. You already noticed the hinges on the back. When you get it open, exercise the right hand lever on top (marked ZZ at bottom and 1-20 at top. If you look just to the right of this lever against the back wall you will see that it moves a little part back and forth into triangle shaped grooves. The part is not going completely into the grooves so drop some oil in there and exercise it a few more times, using your fingers if necessary to make the part move into the triangle grooves at the front and back. After a while it will loosen up where it should operate by itself smoothly . Hope this helps, I know it will.

there is a board inside the foot pedal that goes out sometimes you can check this by flipping the foot pedal upside down and at the top right there is a small hole where you can adjust the speed with a flat head screwdriver but be gentle it breaks easy, if its out you can take it to a bernina dealer and they might have a reapired one or they can send yours off for repair since that part is repair only

Okay, my first take—because it fills bobbins "just fine"—is that the needle bar may be loose. You didn't specify what the service was for: was it just a clean and lube, or did you have a problem? Even with just a clean and lube, the needle-bar height may have needed adjusting, and the tech may not have tightened it securely. Does the needle bar move at all? even just a quick **** or two? If it acts like it is trying to move, but doesn't, that is probably the problem. 
Now, here's the bad news (always seems to be some of that with these kinds of things, eh?): That needle-bar height is critical, and it's not something I can just tell you how to do here. The second bit of bad news is that the problem wasn't discovered for a year, so any service warranty is long expired, by now (unless the owner or manager of the store is your bosom bud, or, you are one of his/her best customers).
The good news is, if the shop is reputable, you could return it to them, explain what happened, and ask how much they would charge just to adjust and secure that needle bar (although the machine could probably use some more oil, by now—because it has just been sitting, which is harder on them than if you use them regularly). If they are like the shop I worked for, they will be glad to give you a slightly discounted rate to preserve their reputation, and hopefully, your business relationship with them. They may even throw some oil on it for the same price. 
One more bit of good news, the Bernina 830 is one fine sewing machine. It is worth fixing, if any machine is. 
Hope this is helpful, and happy sewing!
Ken