Current version states it is not compatible with this version of Firefox Mobile.
Sorry, but in this case you need to wait the version compatible or you will need do downgrade!
Giw do I downgrade until compatible version is updated?
Uninstall your current version and download the previous version or one version that you already used with media hint
But isn't recommended the downgrade, i think better you wait a update of the add on
Are you refering to https://addons.mozilla.org/en-US/firefox/addon/media-hint/ ?
This Media Hint extension is only for the desktop Firefox for Windows, Mac OSX and Linux.
The Extensions for Android version are listed in https://addons.mozilla.org/en-US/android/extensions/ where there is no Media Hint extension found in search.