It's not installing at all, very stressful

I have been trying to add this "Random User Agent" in my firefox but isn't working.
Please know what you will do this.
Thank you

This add-on works well + is Open-Source

Nice, solid user-agent switcher that does its job well. Bravo to Paramtamtam; I applaud you.

Great, works on firefox mobile version and is lightweight.