I am using the LAMP stack, Ubuntu 16.04 LTS version.

I installed WordPress and am trying to install a theme which I have in a .zip file

When I try to install the uploaded theme (where WP clearly says I can upload a .zip file if I have it), I keep getting the following error

"Are you sure you want to do this?

Please try again."

If I try again, the same story repeats.

Is there any way to overcome this issue. I have to be able to install this particular theme on //localhost.

www-data has privileges to create and delete on all sub directories in /var/www/html.