Remove the card from the camera and ( use your older card for this if you have purchased a new one) clean the card metal contacts with alcohol and leave them lightly wet, then work the card in and out of the slot multiple times. Next use canned compressed air to blow out the slot since sometimes the plastic spacers can break off of the cards and block the connection. It is also quite possible that the card is defective (technology of this type does fail occasionally), and while one bad one would is likely, multiple card failures are not, in addition, reset the camera to the default settings again, since a card formatted for another camera can cause the camera operating system to misread.
Please keep in mind that my diagnosis & solutions provided are directly dependent on the accuracy of your description of the problem. As with any "do it yourself" fixes, success is a "team effort", since I can't see or touch the camera, and relies on the customer's manual dexterity and ability to follow the instructions well.
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