My camera stopped saving pictures on the SD card

Hi and welcome to the forum.
I wonder how you formatted the SD card. If it was as an extension to internal then that is likely to be the problem.

Can you check not just how you formatted it but what memory you have left and what camera app you use.

See

You ideally will have

  • more than 4GB left on the main memory and
  • you can see the eject icon to confirm the SD card is portable/external

You will also want the default or open camera app so that you can store on the external SD card or with other apps (Gcam versions) regularly move the photos from the main memory to the SD card