This is usually caused by a malformed metadata block.
There must be no leading space and directives are (usually) case-sensitive.
Good:
// ==UserScript==
// @name YOUR_SCRIPT_NAME
// @include http://YOUR_SERVER.COM/YOUR_PATH/*
// ==/UserScript==
Bad:
// ==UserScript==
// @name YOUR_SCRIPT_NAME
// @include http://YOUR_SERVER.COM/YOUR_PATH/*
// ==/UserScript==
Bad:
//==UserScript==
//@name YOUR_SCRIPT_NAME
//@include http://YOUR_SERVER.COM/YOUR_PATH/*
//==/UserScript==
Bad:
// ==UserScript==
// @name YOUR_SCRIPT_NAME
// @INCLUDE http://YOUR_SERVER.COM/YOUR_PATH/*
// ==/UserScript==
etc.
Also the script options can override what is in your metadata block. Check them or just uninstall and reinstall the script.