Unable to install themes or extensions : Unexpected installation error Review the Error Console log for more details -203


Unable to install themes or extensions :

firefox could not install add-ons

Error Description :

Some times ago i was facing this issue with Mozilla Firefox. I was unable to install any add-on,plugin and theme. I was getting this above message while installing firebug in Firefox. During Installation of .xps file i was getting this -204 error after finishing 98% of installation.

Workaround :

Resolving this issue is not a big deal. You need to follow 3-4 simple steps.

  1. Firstly Close all the instances of Mozilla Firefox.
  2. Restart Mozilla Firefox and then go to Help–>Troubleshooting Information
  3. Click on “Open Containing Folder” Button (Profile Directory).

Open Contaning Folder In Mozilla Firefox

  1. Now inside Folder Delete Following 4 Files –

Delete Following Files from Mozilla
After Deleting these files,Restart Mozilla. Now You will be able to install themes,add-on’s.