Unable to Install Plugin: Membership 2 Pro

Hi,

Can you please assist, we are having trouble installing Membership 2 Pro.

The error message we receive is as follows:
"Installation of Membership 2 Pro failed. Most likely reason for this are wrong folder permissions of your wp-contents folder."

When I check our wp-contents folder the permissions are set to 755.

Can we install this plugin manually? Can you recommend a work around or solution?

Thanks