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That 'SCN' error may refer to a keyswitch scan error... a key switch is stuck down, perhaps? or a connector for the keyboard has been put together incorrectly and so it transmits a similar signal to a stuck-down key.
Anyway, something relative to the keys (and their reporting to the circuitry) is clearly wrong. Reassemble with care, don't wear a sweater of any sort (or a woolen suit coat either - both of those garments can transfer electrostatic discharge into circuitry, ruining it or scrambling it up badly) and touch metal frequently to dissipate static charge before touching anything much. Also, handle fine connectors with care. And don't touch actual circuitry or chips at all if you can help it - handle by the edges of things.
I hope it can be gotten working properly again, with some care to details and with the help of my advice.