It can be possible when IDM finds records in system registry about an old Firefox browser (including Aurora, or Waterfox), which are installed and can be used on your computer. Also you may have different 32 bit and 64 bit Firefox versions.
For example you stopped using, or stopped updating 32 bit version, but actively use 64 bit firefox version.
And conversely if you use an old Firefox and when you restart it, it will have old extension enabled and new extension disabled.
If you don't use your old version of Firefox, you may uninstall it, and then you can re-start IDM using Tasks->Exit menu item, and restart new version of Firefox. After that old "IDM CC" extension should disappear from Firefox settings.
Also please note that when you see both IDM extensions (add-ons) in Firefox list of extensions, and one is disabled while another is enabled, there is nothing wrong with it and you should leave it as it is.