Thanks for the additional data about your environment.
OpenSSH 7.1p1 was released
2015-08-21.
UltraEdit version 14.10.0.1025 was released
2008-07-30. I have not archived version 14.10.0.1018.
Currently newest
PuTTY version 0.71 was released on
2019-03-16 which I assume is used by you.
Do you really think nothing changed between July 2008 and August 2015 (seven years!) regarding to encryption technologies for
SSH File Transfer Protocol?
Many encryption algorithms were added between July 2008 and August 2015 as it can be read in OpenSSH release notes or in PuTTY change log or in
release notes of wodFtpDLX which is the library used by UltraEdit for FTP/SFTP/SSH/Telnet. So I suppose an incompatibility in SSH encryption between wodFtpDLX version used by UltraEdit version 14.10.0.1018 and OpenSSH 7.1p1 used by the SFTP server.
My recommendation is paying for an upgrade to currently latest UltraEdit v26.10.0.38 which is installed with latest available version of wodFtpDLX.
I have helped once a user to update just the three files
wodCertificate.dll,
wodFtpDLX.dll and
wodTelnetDLX.ocx installed with UE v16.30 by the three files with same name installed with 32 bit UE v24.20, see my post on
UltraEdit for Windows v16.xx won't connect to Raspberry Pi with SSH (solved) for details.
But I really doubt that
wodCertificate.dll (DLL version 1.7.6.5),
wodFtpDLX.dll (DLL version 3.5.5.755) and
wodTelnetDLX.ocx (DLL version 2.5.6.179) of 32 bit UltraEdit version 26.10.0.38 are 100% compatible with
wodCertificate.dll (DLL version 1.4.0.4),
SftpDLL.dll (DLL version 3.2.3.73) and
wodTelnetDLX.ocx (DLL version 2.3.6.107) of UltraEdit version 14.10.0.1018. With UltraEdit v14.20 the DLL file
SftpDLL.dll with
wodSFTP API library was replaced by DLL file
wodFtpDLX.dll (DLL version 2.8.6.439) with
wodFtpDLX Component library. So I am quite sure that the library files of 32 bit UE v26.10.0.38 for FTP/FTPS/SFTP are not compatible with the library files of UE v14.10.0.1018, especially because of one library is a completely different one.
I think, there is no chance to get UltraEdit v14.10.0.1018 working with your SFTP server because this version of UltraEdit is really too old.