Which Hotline client are you using out of interest? I have nostalgic memories of using Hotline as a teenager and just assumed all clients are now dead in the water.
Usually Hotline 1.8.5 on Windows, Nostalgia or Frogblast on OSX. 1.2.3 on OS9 or earlier. hx on bsd/linux CLI :) I usually point people here to find a Hotline client to use: https://preterhuman.net/gethotlinekdx.php