Membership Premium Doesn't show

I have added this plugin into wordpress installations. I have spent the last 20 hours debugging what could have went wrong and where it may have went wrong.

The problem:

When I activate Membership Premium, I am presented with nothing. Just tells me plugin is activated yet there is no sidebar or top menu bar as there should be.

Debugging:

I have ran with debugging mode enabled I navigated to /wp-admin/admin.php?page=membership&action=activate and was presented with "You do not have sufficient permissions to access this page." (I am admin).

I then installed wordpress fresh and used a new database, installed the plugin, shown up fine. Could have complete access and enabled everything perfectly. I then imported the posts and users from the old database which once again completely broken the script.

I recreated another database and made posts on there with membership enabled and it worked fine. I am wondering if this plugin only works when you have no posts/pages to begin with.

Can any tech advise me?