Failing importing ECDSA and ed25519 public keys from SFTP server

Hi guys

I just want to ask if anybody encountered my same problem , basically I'm configuring a push receiver to forward CDR to an external SFTP server , for do that I need to import , as known host , the public key of it . I've no problem to import RSA , but when I try to import ECDSA and ed25519 keys an error is reported . I've correctly converted in RFC4716 on the linux system where the SFTP resides with the command :

[root@smpp-kannel ssh]# ssh-keygen -e -f ./ssh_host_ecdsa_key.pub

---- BEGIN SSH2 PUBLIC KEY ----

Comment: "256-bit ECDSA, converted by root@smpp-kannel from OpenSSH"