Either you modified the wrong file, or you modified the right one, but failed to properly upload it to your site. In the latter case, you might have uploaded to the wrong directory, or the file is read-only (such as 444 permissions) and the upload failed to overwrite it. Go into your control panel (cPanel or LPCP?) File Manager and take a look at the file you think you modified, and see if your changes are really there.
There is one other possibility: you did successfully modify the right file, but it's still using a cached version. In your browser, hit Ctrl+F5 on the page where you get the message, to force a fresh page reload. If still no change, SMF has its own caching that you may need to force a refresh on. You'll have to ask someone SMF-savvy about that. If you're running SMF you ought to be signed up on the Simple Machines Forum and asking SMF-specific questions there.