Hi, I purchased two Samsung A21s in August for myself and my wife. Sd cards (SanDisk) from the old phones used which I reformatted before inserting. Worked fine for approx a month and then got the message 'can't write to sd card message', lost access to a number of photos which was annoying. The same issue occurred with my wife's phone at the same time. I reformatted the sd cards which solved the problem for a short while then it happened again in both phones. It is clear to me that it is an operating system issue. It has put me off buying a Samsung in the future. The reformatting solution mentioned works but only for a short while.
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