Looks like you're still using old csgo files.
1) Go in that discussion thread, and download what .zip file, and copy 2 files from linux32 folder, and start the server.
2) Try start ./steamcmd.sh to update all steam files and exit from steam login console. In WinSCP options, make visible all hidden folders. Go where did you downloaded ./steamcmd (i downloaded in /root folder) and find hidden folder called ".steam/sdk32/steamclient.so" and edit link to updated steamclient.so for example /root/linux32/steamclient.so
And start the server.
Just downloaded clean CS:S server on my another linux VPS for testing. Changed 2 files (from updated ./steamcmd linux32 folder), added lines 3 lines and added on my Dedicated server CS:S ip address in sourcebans for the test. With challenge didn't show the server, without it - shows... Using updated SB++ from here https://github.com/sbpp/sourcebans-pp/