What specific make and type of SD card and reader are you using to connect to the IDE port of your Amiga 1200?
I have a suspicion that it might be because not all types of card and/or reader have proved to be compatible with the Amiga's IDE port.
Edit: Don't worry, it's unlikely that you will have damaged anything. Does the original hard drive still work satisfactorily when reconnected to the Amiga?
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