ReadonlyThe mnemonic did not have a supported number of words (12 or 24 for regular and 22 for legacy).
The checksum encoded in the mnemonic did not match the checksum we just calculated for that mnemonic.
24-word mnemonics have an 8-bit checksum that is appended to the 32 bytes of source entropy after being calculated from it, before being encoded into words.
This could happen if two or more of the words were entered out of the original order or replaced with another from the standard word list (as this is only returned if all the words exist in the word list).
The mnemonic contained words which were not found in the word list.
Possible statuses for Mnemonic#validate().