Garry's Mod server is not in the browser or players see errors

Work through these in order. The console tells you more than the game does.

1. Prove the server works

Open the game console and run connect IP:Port with the details from your panel. If that works, the server is fine and the rest is about the browser.

2. sv_lan must be 0

Set sv_lan 0 in garrysmod/cfg/server.cfg and restart. With it set to 1 the server never advertises itself and refuses internet connections.

3. Set a game server token

A Steam game server token improves how the server is listed and is required for some workshop features. Create one on your own Steam account and add sv_setsteamaccount YOURTOKEN to server.cfg. Restart and read the console for the line confirming the server logged in to Steam.

4. The workshop collection is not downloading

• The collection must be public.
• A Steam Web API key must be set as well as the collection ID, or the download is skipped.
• Read the console during boot. Each item is listed as it downloads, so anything missing there was never fetched.
• A very large collection makes the first start slow. Let it finish rather than restarting.

5. Players see missing textures and errors

• Content that only exists on the server produces errors on the client. Use a workshop collection so players get the same files.
• Ask players to subscribe to the collection and let it download before joining.
• Some addons need the original game content, such as Counter-Strike: Source, on both the server and the client. Those errors are not a server fault.

6. The server crashes on map change

• A broken addon or gamemode is the usual cause. Read the console for the last Lua error before the crash.
• Remove the last addon you added and restart to test.
• If the console shows the process being killed rather than a Lua error, the server ran out of memory. Reduce the addon load or move to a larger plan.

Open a ticket from Support in the Client Area with the last 50 lines of console output if none of this fits.