SRCDS not receiving connections on the public web

My Garry's Mod Source DS can connect over LAN, but not externally. Ports 27015-27016 are opened and directed towards the machine running it. I can telnet into it and canyouseeme can see it running, but the Source client can't connect for some reason. Any idea of what can be going on? I'm running it on Fedora Linux Server with the firewall disabled. What's weird is that I'm hosting a web server (UDP + TCP port 80) and Mumble server (UDP + TCP port 64738) on it as well, and both are publicly accessible.

Here's my server.cfg if needed:

"ip"                "[external IP]"
"hostname"          "memes"
"maxplayers"        "12"
"sv_password"       "[password]"
"sbox_noclip"       "1"
"sbox_maxprops"     "4000"
"sbox_maxeffects"   "4000"
"sbox_maxemitters"  "4000"
"sbox_maxthrusters" "4000"
"sbox_maxsents"     "4000"
"sv_loadingurl"     "[loading page]"

And the script I use to start it up:

./srcds_run -game garrysmod +map gm_construct +maxplayers 12 -authkey [authkey] +host_workshop_collection [some addon IDs]