You might need to confirm which keys you have attached to your github account. Github provides a list of your keys with the associated fingerprints. If you have a public key on your machine you can see what fingerprint it has with:
> ssh-keygen -lf ~/.ssh/id_rsa.pub 4096 SHA256:/6Rat4zVZ0auHEwWtF4QG8NA0j4NAKWisFuXV0ZP5zk firstname.lastname@example.org (RSA)
Github displays an md5 fingerprint rather than a sha256 fingerprint. You can use the
-E flag to choose a specific hash type.
> ssh-keygen -E md5 -lf ~/.ssh/id_rsa.pub 4096 MD5:e3:19:85:1c:8a:31:0f:4b:de:cb:6d:a7:64:b4:4e:e7 email@example.com (RSA)