SFTP connection failed : Server signature is not valid

Hi, We have been trying to connect to an external SFTP connection but we get an error saying that "Server signature is not valid" Error: SFTP connection failed: SFTP.XXXXXX.COM/ | | Server signature is not valid. at ComponentPro.Net.Sftp.c_d8db87dc(String , Int32 , SecureShellConfig , AsyncOperation ) at ComponentPro.Net.Sftp.Connect(String serverName, Int32 serverPort) at En.Logic.Transmission.CompProSFTP.Connect(Sftp sftp, ITransmissionSettings transmissionSettings) in D:\jenkins\workspace\Exports\assemblies\En.Logic\Transmission\CompProSFTP.cs:line 216 Any help is appreciated. Thanks!