Spark Hosting WordPress Theme fail to install

I bought Spark - Responsive WHMCS Hosting WordPress Theme,
I follow the instructions:
Appearance->Upload Theme->ChooseFile: spark-theme-v2.0.zip , click button [Install Now]

Screen display:

Are you sure you want to do this?
Please try again.

Nothing happen. I try many times without improvement.
I would be very appreciate if someone can help

The error: "Are you sure you want to do this?"
If you are installing your theme from the WordPress theme installer, but get a message that says “Are you sure you want to do this?”, most likely your web server is configured with PHP settings that are too low to allow the theme ZIP file to upload.
Specifically, PHP is configured to a maximum file upload size limit at 8 megabytes or less. The theme ZIP is about 13.7 megabytes in size. Thus, the web server is rejecting the upload. WordPress is giving you a rather ambiguous message in response. This is not a theme fault or bug.

You can either get your web host to increase your PHP limits. Some hosting allows you change PHP values from htacess or PHP.ini Please check your help documents from provider.

Recommended PHP configuration limits are as follows:

max_execution_time = 300
post_max_size = 20M
upload_max_filesize = 8M

I update php configuration as follows:

max_execution_time = 300
post_max_size = 20M
upload_max_filesize = 15M

I get this message:
The uploaded file could not be moved to wp-content/uploads/2017/06.

Still not successful

The “are you sure” error is your hosting - use FTP and it will work