Cannot upload package ("signature made by unknown entity")

$ dput autodeb *changes
Uploading redis using https to autodeb (host: auto.debian.net; directory: /upload)
running allowed-distribution: check whether a local profile permits uploads to the target distribution
running checksum: verify checksums before uploading
running suite-mismatch: check the target distribution for common errors
running gpg: check GnuPG signatures before the upload
Uploading redis_4.0.10-2.dsc
HTTP Error 301: Moved Permanently

$ FILE=redis_4.0.10-2_amd64.changes ; curl -w "\n" -X PUT -T $FILE https://auto.debian.net/upload/$FILE
{"message":"could not identify the signer: could not check signature: could not check signature: openpgp: signature made by unknown entity"}

$ gpg --verify *.changes
gpg: Signature made Tue 31 Jul 2018 20:38:10 CST
gpg:                using RSA key C2FE4BD271C139B86C533E461E953E27D4311E58
gpg: Good signature from "Chris Lamb <chris@chris-lamb.co.uk>" [unknown]
gpg:                 aka "Chris Lamb <lamby@gnu.org>" [unknown]
gpg:                 aka "Chris Lamb <lamby@debian.org>" [unknown]
gpg: WARNING: This key is not certified with a trusted signature!
gpg:          There is no indication that the signature belongs to the owner.
Primary key fingerprint: C2FE 4BD2 71C1 39B8 6C53  3E46 1E95 3E27 D431 1E58

This is the key that is configured on salsa: https://i.imgur.com/qgv1Yil.png. Any ideas?