the radio isn't working ingame, the HTML MOTD is enabled, I checked that cl_allowdowload is 1, I even tried installing flashplayer, the radio doesnt work in any server at all
It used to work before but now the MOTD uses Steam's chromium based browser which is probably not available on no-Steam.
Do you have steam installed? If not, install it, then add CSS as a nonsteam game to the library(this way you can open the steam overlay), then go to https://hellfm.co.uk