I have been moving round trying to use the manual method still do not work, what I did was to delete it to see if I could download it back (add) but it refuses. Seems there is no hope for that, I am only window store now downloading my firefox to see if I can use it on that browser.
Have you tried downloading it from here?
You can try re-downloading and installing this [
Extension] by enabling Developer Mode, and let me know the results.
Then drag&drop it (with developer mode enabled) in the extensions management page
chrome://extensions/Look here, this is what I am seeing over here and there is nothing displaying after I finished downloading the extension as instructed.

This is after downloading the extension.. from my download history..

Then this is the extension management page, the developer mode is already turned on and yet the extension do not display there.
Edit..

It's working.. I drag and drop to the extension management page.. and I have enabled all the features, everything is now back.
Thank you boss man..

I was trying again and again for the past few days. But I couldn't download it using Chrome browser. After seeing this today, I changed the browser and it downloaded. I was really having a lot of trouble for the past few days. Just for writing this one:
Thank you all from the bottom of my heart .