Server unexpectedly closed network connection
I have a script that opens this WinSCP connection and uploads a file to vendor. This has been working without issues for years. For what ever reason it has stopped working in April. Below is the error log I'm getting when I try to connect. Can anyone tell me if this is on vendor side or my server?
. 2021-10-19 15:40:12.337 --------------------------------------------------------------------------
. 2021-10-19 15:40:12.337 WinSCP Version 5.5.4 (Build 4433) (OS 6.3.9600 - Windows Server 2012 R2 Datacenter)
. 2021-10-19 15:40:12.337 Configuration: C:\xxx\WinSCP.ini
. 2021-10-19 15:40:12.337 Local account: xxxx\xxxxxxx
. 2021-10-19 15:40:12.337 Working directory: C:\xxx
. 2021-10-19 15:40:12.337 Process ID: 1840
. 2021-10-19 15:40:12.337 Command-line: "C:\xxx\WinSCP.exe"
. 2021-10-19 15:40:12.337 Time zone: Current: GMT-5, Standard: GMT-6 (Central Standard Time), DST: GMT-5 (Central Daylight Time), DST Start: 3/14/2021, DST End: 11/7/2021
. 2021-10-19 15:40:12.337 Login time: Tuesday, October 19, 2021 3:40:12 PM
. 2021-10-19 15:40:12.337 --------------------------------------------------------------------------
. 2021-10-19 15:40:12.337 Session name: xxxxxxxxx@xxxxxx.com (Site)
. 2021-10-19 15:40:12.337 Host name: sftp.xxxxxxx.com (Port: 22)
. 2021-10-19 15:40:12.337 User name: xxxxxxxx (Password: Yes, Key file: No)
. 2021-10-19 15:40:12.337 Tunnel: No
. 2021-10-19 15:40:12.337 Transfer Protocol: SFTP (SCP)
. 2021-10-19 15:40:12.337 Ping type: -, Ping interval: 30 sec; Timeout: 15 sec
. 2021-10-19 15:40:12.337 Proxy: none
. 2021-10-19 15:40:12.337 Send buffer: 262144
. 2021-10-19 15:40:12.337 SSH protocol version: 2; Compression: No
. 2021-10-19 15:40:12.337 Bypass authentication: No
. 2021-10-19 15:40:12.337 Try agent: Yes; Agent forwarding: No; TIS/CryptoCard: No; KI: Yes; GSSAPI: Yes
. 2021-10-19 15:40:12.337 GSSAPI: Forwarding: No; Server realm:
. 2021-10-19 15:40:12.337 Ciphers: aes,blowfish,3des,WARN,arcfour,des; Ssh2DES: No
. 2021-10-19 15:40:12.337 SSH Bugs: A,A,A,A,A,A,A,A,A,A
. 2021-10-19 15:40:12.337 Simple channel: Yes
. 2021-10-19 15:40:12.337 Return code variable: Autodetect; Lookup user groups: A
. 2021-10-19 15:40:12.337 Shell: default
. 2021-10-19 15:40:12.337 EOL: 0, UTF: 2
. 2021-10-19 15:40:12.337 Clear aliases: Yes, Unset nat.vars: Yes, Resolve symlinks: Yes
. 2021-10-19 15:40:12.337 LS: ls -la, Ign LS warn: Yes, Scp1 Comp: No
. 2021-10-19 15:40:12.337 SFTP Bugs: A,A
. 2021-10-19 15:40:12.337 SFTP Server: default
. 2021-10-19 15:40:12.337 Local directory: C:\Users\xxxxxxxxxx\Documents, Remote directory: /, Update: Yes, Cache: Yes
. 2021-10-19 15:40:12.337 Cache directory changes: Yes, Permanent: Yes
. 2021-10-19 15:40:12.337 DST mode: 1; Timezone offset: 0h 0m
. 2021-10-19 15:40:12.337 --------------------------------------------------------------------------
. 2021-10-19 15:40:12.415 Looking up host "sftp.xxxxxxxxxx.com"
. 2021-10-19 15:40:12.415 Connecting to xx.xx.xxx.xx port 22
. 2021-10-19 15:40:12.508 Server version: SSH-2.0-WS_FTP-SSH_8.7.0.105
. 2021-10-19 15:40:12.508 Using SSH protocol version 2
. 2021-10-19 15:40:12.508 We claim version: SSH-2.0-WinSCP_release_5.5.4
. 2021-10-19 15:40:12.540 Doing Diffie-Hellman group exchange
. 2021-10-19 15:40:12.680 Server unexpectedly closed network connection
. 2021-10-19 15:40:12.680 Knocking FTP port.
. 2021-10-19 15:40:14.681 FTP port did not open.
* 2021-10-19 15:40:14.728 (EFatal) Server unexpectedly closed network connection.