Hello Setti,
I have added my CS 1.6 server to your server list using: http://css.setti.info/#addserver
And it accepted my server using both V48 and NSD methods saying this;
[Wed Apr 3 08:22:55 2019]: Verifying 35.240.208.239:27015 (35.240.208.239:27015) [Wed Apr 3 08:22:56 2019]: Got KEY for v48 test (hl1) from 35.240.208.239:27015 [Wed Apr 3 08:22:56 2019]: Server reply: B 4 54.221.47.60:40462 0 1812 [Wed Apr 3 08:22:56 2019]: OK. Server accepted me.
[Wed Apr 3 08:25:10 2019]: Verifying 35.240.208.239:27015 (35.240.208.239:27015) [Wed Apr 3 08:25:10 2019]: Got KEY for NSD test (hl1) from 35.240.208.239:27015 [Wed Apr 3 08:25:10 2019]: Server reply: B 5 107.20.130.142:35729 0 1812 [Wed Apr 3 08:25:10 2019]: OK. Server accepted me.
But it's still not visible here: http://css.setti.info/servers/full/ or even in-game server list.
I hope you will help. Thank you!