Host key verification failed

I recently downloaded the latest version of SmartFTP library to fix a problem with one of my host sites. Now, one that has been working fine no longer connects. Here is the log:
 
2015-05-08T12:17:35 SmartFTP FTP Library 4.0.462.0
2015-05-08T12:17:41 Resolving host name "<ftphost>.com"
2015-05-08T12:17:41 Connecting to <ip> Port: 22
2015-05-08T12:17:41 Connected to <ftphost>.com.
2015-05-08T12:17:41 SSH protocol version reply. Client Id: SSH-2.0-SmartFTP
2015-05-08T12:17:41 SSH-2.0-6.4.5.90 SSH Tectia Server
2015-05-08T12:17:41 Starting SSH session. Remote Id: "SSH-2.0-6.4.5.90 SSH Tectia Server"
2015-05-08T12:17:41 Server Algorithm Suite
Key Exchange: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
Server Host Key: ssh-dss,ssh-dss-sha256@ssh.com
Client to Server Encryption: aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,seed-cbc@ssh.com,crypticore128@ssh.com
Server to Client Encryption: aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,seed-cbc@ssh.com,crypticore128@ssh.com
Client to Server HMAC: hmac-sha1,hmac-md5,crypticore-mac@ssh.com
Server to Client HMAC: hmac-sha1,hmac-md5,crypticore-mac@ssh.com
Client to Server Compression: none,zlib
Server to Client Compression: none,zlib
2015-05-08T12:17:41 Selected Algorithm Suite
Key Exchange: diffie-hellman-group-exchange-sha256
Server Host Key: ssh-dss
Client to Server Encryption: aes128-ctr
Server to Client Encryption: aes128-ctr
Client to Server HMAC: hmac-sha1
Server to Client HMAC: hmac-sha1
Client to Server Compression: zlib
Server to Client Compression: zlib
2015-05-08T12:17:41 Client Algorithm Suite
Key Exchange: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
Server Host Key: ssh-ed25519,x509v3-ecdsa-sha2-nistp256,x509v3-ecdsa-sha2-nistp384,x509v3-ecdsa-sha2-nistp521,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,x509v3-rsa2048-sha256,x509v3-sign-rsa,x509v3-sign-dss,ssh-rsa,ssh-dss
Client to Server Encryption: aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
Server to Client Encryption: aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr,aes128-cbc,aes192-cbc,aes256-cbc,3des-cbc
Client to Server HMAC: hmac-sha1,hmac-sha2-256,hmac-sha2-512
Server to Client HMAC: hmac-sha1,hmac-sha2-256,hmac-sha2-512
Client to Server Compression: zlib@openssh.com,zlib,none
Server to Client Compression: zlib@openssh.com,zlib,none
2015-05-08T12:17:41 Key Exchange Algorithm: diffie-hellman-group-exchange-sha256
2015-05-08T12:17:42 Host key verification failed.
2015-05-08T12:17:42 Client closed the connection.
 
I tried the same host, login ID and password on SmartFTP Client and it works fine:
 
[12:15:18] SmartFTP 6.0.2136.0
[12:15:18] 3>Resolving host name "<ftp host>.com"
[12:15:18] 3>Connecting to <ip> Port: 22
[12:15:19] 3>Connected to <ftphost>.com.
[12:15:19] 3>SSH protocol version reply. Client Id: SSH-2.0-SmartFTP
[12:15:19] 3>SSH-2.0-6.4.5.90 SSH Tectia Server
[12:15:19] 3>Starting SSH session. Remote Id: "SSH-2.0-6.4.5.90 SSH Tectia Server"
[12:15:19] 3>Server Algorithm Suite
             Key Exchange: diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group14-sha1,diffie-hellman-group1-sha1
             Server Host Key: ssh-dss,ssh-dss-sha256@ssh.com
             Client to Server Encryption: aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,seed-cbc@ssh.com,crypticore128@ssh.com
             Server to Client Encryption: aes128-cbc,aes192-cbc,aes256-cbc,aes128-ctr,aes192-ctr,aes256-ctr,3des-cbc,seed-cbc@ssh.com,crypticore128@ssh.com
             Client to Server HMAC: hmac-sha1,hmac-md5,crypticore-mac@ssh.com
             Server to Client HMAC: hmac-sha1,hmac-md5,crypticore-mac@ssh.com
             Client to Server Compression: none,zlib
             Server to Client Compression: none,zlib
[12:15:19] 3>Selected Algorithm Suite
             Key Exchange: diffie-hellman-group-exchange-sha256
             Server Host Key: ssh-dss
             Client to Server Encryption: aes128-ctr
             Server to Client Encryption: aes128-ctr
             Client to Server HMAC: hmac-sha1
             Server to Client HMAC: hmac-sha1
             Client to Server Compression: zlib
             Server to Client Compression: zlib
[12:15:19] 3>Client Algorithm Suite
             Key Exchange: curve25519-sha256@libssh.org,ecdh-sha2-nistp256,ecdh-sha2-nistp384,ecdh-sha2-nistp521,diffie-hellman-group-exchange-sha256,diffie-hellman-group-exchange-sha1,diffie-hellman-group1-sha1,diffie-hellman-group14-sha1
             Server Host Key: ssh-ed25519,x509v3-ecdsa-sha2-nistp256,x509v3-ecdsa-sha2-nistp384,x509v3-ecdsa-sha2-nistp521,ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,x509v3-rsa2048-sha256,x509v3-sign-rsa,x509v3-sign-dss,ssh-rsa,ssh-dss
             Client to Server Encryption: aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr
             Server to Client Encryption: aes128-gcm@openssh.com,aes256-gcm@openssh.com,aes128-ctr,aes192-ctr,aes256-ctr
             Client to Server HMAC: hmac-sha1,hmac-md5,umac-64@openssh.com,hmac-sha2-256,hmac-sha2-512
             Server to Client HMAC: hmac-sha1,hmac-md5,umac-64@openssh.com,hmac-sha2-256,hmac-sha2-512
             Client to Server Compression: zlib@openssh.com,zlib,none
             Server to Client Compression: zlib@openssh.com,zlib,none
[12:15:19] 3>Key Exchange Algorithm: diffie-hellman-group-exchange-sha256
[12:15:20] 3>Server "ssh-dss" host key fingerprint: 28:df:c1:5e:fc:44:cc:2c:5a:43:1a:70:ad:b6:50:1e
[12:15:20] 3>Key exchange completed.
[12:15:20] 3>Requesting service "ssh-userauth".
[12:15:20] 3>RTT: 199.060 ms
[12:15:20] 3>Authentication request. Method: none
[12:15:20] 3>Received authentication banner message.
[12:15:20] 3>Server supported authentications: password,publickey,keyboard-interactive
[12:15:20] 3>Authentication request. Method: password
[12:15:20] 3>User authentication successful.
[12:15:20] 3>SSH session established.
[12:15:20] 3>Detected Server Software: SSH Communications Security Tectia Server
[12:15:20] 3>Opening channel 0.
[12:15:20] 3>Channel successfully opened (Local=0, Remote=0).
[12:15:20] 3>Requesting subsystem "sftp" (Local=0, Remote=0).
[12:15:21] 3>Sending FXP initialization. Protocol version=6.
[12:15:21] 3>SFTP protocol version 3
[12:15:21] 3>Resolving path ".".
[12:15:21] 3>Path successfully resolved to "/".
[12:15:21] 3>Resolving path "/".
[12:15:21] 3>Path successfully resolved to "/".
[12:15:21] 3>Reading directory "/".
[12:15:21] 3>620 bytes transferred. (3.75 KB/s) (161 ms)
[12:15:21] 3>Closing file handle.
[12:15:21] 3>Directory listing complete.
 
Can you see anything I'm doing wrong? It worked fine until I installed the latest version of SmartFTP library.
 
Thanks