If you aren't tracking an individual, you can't encrypt a message

You have to be tracking a user to encrypt messages for them through your software and website. If you aren't it just says the header was not found upon attempting decryption.

Start by reproducing the encryption and decryption flow in the Keybase software and website when the recipient is not being tracked. Trace the resulting “header was not found” message and define done as correctly handling this case with an appropriate outcome instead of the misleading decryption error.

Written by the indexing model from the issue text.