I had intermittent problems with my SIM and SD cards not being recognized. I noticed they did not fit very tightly in their slots. I had a couple of old nano SIM cards so I glued them to the back of my SIM and SD cards an now they fit very snugly and always work. If you don't have extra SIM cards, I think you can cut a little chunk off the punch-out card which used to hold your SIM card.
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