You said you converted them with Calibre, but have you tried transferring them to the Kindle with Calibre?
The other thing is that you said you reset the Kindle but did you erase the Kindle documents folder contents before you tried transferring the books? You can do that via your PC/Mac. When all else has failed with strange actions on my Kindle (and there've been quite a few) THAT has always worked for me.
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