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.

Works very well, but wish it had the ability to set a custom user agent for a specific website. Meaning that user agent was only used on that site, and all other sites are not effected. At least i can't get it to work like this, maybe I'm doing something wrong though.