Installation of WP Smush Pro failed

I couldn't install WP Smush Pro, I'm getting this error message:
"Installation of WP Smush Pro failed. Most likely reason for this are wrong folder permissions of your wp-contents folder."

I found that WP Defender has made some modifications in .htaccess file. Maybe this is related to the problem but I'm not sure.

Just let me know if you need me to grant access to my wordpress dashboard ok?

Thanks!