Could that person try to set the volume of other players and try again?

Causes a different error:

[ERROR] gamemodes/terrortown/gamemode/client/cl_voice.lua:499: bad argument #1 to 'SetVoiceVolumeScale' (number expected, got nil)

1. SetVoiceVolumeScale - [C]:-1
2. UpdatePlayerVoiceVolume - gamemodes/terrortown/gamemode/client/cl_voice.lua:499
   3. DoClick - gamemodes/terrortown/gamemode/client/vgui/cl_sb_row.lua:337
   4. OnMouseReleased - lua/vgui/dlabel.lua:237
   5. unknown - lua/vgui/dimagebutton.lua:103

that one should also be solved via #1335

Are you playing a dedicated server?
Are you playing peer to peer?

Is the error in other client's consoles? Is the error in the server's console? What color is the error?

Is one of the players on LAN? Are they authorized on steam?
The system uses SteamID64 so multiple users on the same account may be impacted by this behavior.

It's very hard to pinpoint a cause without more information about how this is being played or getting that user's steamid64.

Dedicated server run from my machine.
Console log when player attempts to join, same errors are seen in their console, but is not seen by others in the server.
User's SteamID64 is 76561198177059830