The host key was not replaced

  ✗ The server's host key changed. sealup.yml was not changed.
    sealup.yml (line 4) expects one key; ssh.example.com sent another:
      expected  ED25519 SHA256:…
      received  ED25519 SHA256:…

    More: sealup.dev/e/host-key-not-replaced

Exit code: 4. Server changed: no.

What happened

sealup keyscan found another key on the server than the one saved, and kept the saved one: you answered no, or it ran without a terminal.

Why

Either your host moved the site to a new server, or someone between you and the server is posing as it. sealup never replaces a key without a yes on a terminal. A deploy stops before logging in while the server shows the other key.

The fix

Ask your host for the server’s fingerprint. If it is the received one, run on a terminal and answer yes, then commit sealup.yml:

sealup keyscan production