Run the stud finder over the ceiling in that area. The magnet technique is slow.

Best Stud Finder
Stud finder doesn t work. If it doesnt find a joist measure 24 inches from the wall and try that area instead. One way i would try is an educated guess exploratory hole method try locating a stud with a stud finder on the same wall but away from the problem area. The first technique works but it damages the wall. Stud finder tips once youve identified your stud move away then come back and find it again at a different height. The stud finder doesnt work very well anywhere in my house. If your stud finder seems to be picking up things between the studs it could be detecting metal or plastic plumbing components electrical boxes or wiring or metal ductwork.
If you cant see it there then buy a new finder. This is an indication that the battery in your electronic stud finder has discharged. Now find the next. Device does not switch on. 1 studfinder does not work test on an exterior wall studs should be 16inches apart or less. Once you get close to one theres a simple and reliable way to find and mark both side edges of the stud so you can drill or anchor into its center.
Try using the stud finder at a higher point on the wall or a lower. If youre using an edge finder be sure. The magnet would help you find nails that had been driven into a stud. If your stud finder is not working properly it may not be your stud finder. If your stud finder has rechargeable batteries recharge them or inset new batteries if it uses disposable ones. Some stud finders are surprisingly sensitive to battery charge.
Before there were stud finders either you pounded a small nail into the wall until you hit a stud or you used a small pivoting magnet. If yours was working yesterday and isnt today try. Then if you have a little bit of faith that your builder followed the standard 16 stud spacing measure over and drill at 16 intervals. Heres how you should go about troubleshooting your glitch electronic stud finder. They give you. It may actually be your wall.
If you dont have a handy stud finder tool to locate wall studs youll just have to do it the old fashioned way using one of several time tested methods. Older houses that were built with lath and plaster instead of sheet rock often have too much inconsistency in the walls for the detector to work reliably. When it lights up it has reached the edge of a joist. Electronic stud finders changed all that.