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Why didn't you read the highlighted sticky at the top of the forum - that says read this before posting a programming question. Someone took the time to write it, in the hope that people find it helpful.
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Please post your code in `` tags. It means people can read it.
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In C++, (and the arduino language is C++), a value thus 'a' is a character literal. A value this '0x41' is also a character literal. I think your variable holding (the character literal) might be an signed char, which cannot store more than 128, which might explain the error. I cannot read the .png well so am guessing a bit.
4 Do you expect the keypad to return a '2', a '0', a '0'? (3 characters), or will it return (integer) 200 if you press 2,0,0?
What does the documentation for the library say?
5 Put some debug printing in, to see what the keypad is actually giving.
6 You might want to set the LED pin to an output.