Several years ago WhatsApp Messenger used .crypt8 files instead of the current .crypt 12. Many users are since then trying to recover the chat history from these files and save these in one of the common formats, typically HTML:
You have to first get the original crypt version from your crypt8 file and then proceed to extract the chat history with a program known as WhatsApp Xtract, which is more or less what crypt8 to crypt conversion is about.
Open CRYPT8 file Open CRYPT fileOnline service for WhatsApp databases