Probably someone previously in this reader formatted the internal memory. You need to reinstall the diagnostic system. Unfortunately, updates from Amazon do not include it. You can find them here:
https://www.mobileread.com/forums/sh...d.php?t=342535
You need to use fastboot for kindle. Search the threads because it has been described many times.
If you only want to jailbreak, it may be easier to upload some older software that you will break without access to diagnostics and then update to the version that suits you.