Crash plugin: "Error detected in plugin startup (see error logs)"

[Koshchey-the-Deathless]

L 03/06/2026 - 19:01:19: SourceMod error session started
L 03/06/2026 - 19:01:19: Info (map "c1m1_hotel") (file "/home/.../serverfiles/left4dead2/addons/sourcemod/logs/errors_20260306.log")
L 03/06/2026 - 19:01:19: [SM] Exception reported: Invalid convar handle 0 (error 4)
L 03/06/2026 - 19:01:19: [SM] Blaming: [l4d2][plugin_name].smx
L 03/06/2026 - 19:01:19: [SM] Call stack trace:
L 03/06/2026 - 19:01:19: [SM] [0] GetConVarInt
L 03/06/2026 - 19:01:19: [SM] [1] Line 889, D:/.../.../.../scripting/[l4d2][plugin_name].sp::OnPluginStart
L 03/06/2026 - 19:01:19: [SM] Unable to load plugin "[l4d2][plugin_name].smx": Error detected in plugin startup (see error logs)
L 03/06/2026 - 19:01:41: Error log file session closed.

In my base plugin for line 889:
ConVarRef_SvMaxPlayers = FindConVar("sv_maxplayers");

I can only use "L4DToolZ v2.0.1". It works fine, with no errors.