@fwiwjeannie , Jeannie, First try another card in case that card has a damaged edge. If different card not locking, look in the SD slot/port to see if there is and debri keeping the card from looking in place and if you see some very carefully pick it out with perhaps a tooth pick. If no debri found the slot lock pin/spring may be damaged and may need replaced or repaired. The link below shows how to disassemble the camera to access the SD card slot to have a closer look if need be. If not wanting to attempt the repair your self perhaps have a good local camera shop have a look/estimate repair as they may be familiar with this issue and have quick fix/parts. Good luck. I hope this helped you out, if so let me know by pressing the helpful button.
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