Membership Pro activation problem

I have instaled the Membership Pro pluging and I have activated from the Plugins section of Wordpress Dashboard, but after activating it, it does not appear installed. And a warning is displayed that says: "The Membership plugin is not enabled. To ensure your content is protected you should enable it".

If I click on the link "enable it", a blank page is openned with the following message: "You do not have sufficient permissions to access this page."

I do I solve this? Tks a lot.-