Cannot add public key

My account is: https://keybase.io/djoerd I am "a mystery user with no key"

When I add my PGP public key, Keybase says:

Error: cannot have 2 primary keys

What's wrong?

The issue names no repository file, test, or entry point. Start by reproducing the public-key addition failure for the linked Keybase account and trace the code handling primary-key validation. Done means identifying why the account rejects the key and confirming that the reported error no longer occurs without breaking existing key validation.

Written by the indexing model from the issue text.