The user is not Administrator of any Fan Page on Facebook

If you are an admin of a Fan Page already and getting this error, 

Ensure that you are login with your Facebook account associated with Pagenisis. Go to your profile, mouse over the field Token and click on the icon to refresh your token. After that try to see if it's showing your Fan Pages. As seen on the screenshot below in a red box.

 

Other reason is, you are not an admin of any page or you don't have a Fan Page yet. 

How do I create a Page?

To create a Page:

1. Go to facebook.com/pages/create
2. Click to choose a Page category
3. Select a more specific category from the dropdown menu and fill out the required information
4. Click Get Started and follow the on-screen instructions

Reference: https://www.facebook.com/help/104002523024878

If you like to post in behalf of the page owner, you can ask them to promote you as an admin.

How do I give someone a role on my Page?

You'll need to be an admin to give someone a role on your Page. If you're an admin:

1. Click Settings at the top of your Page.
2. Click Page Roles in the left column.
3. If the person is your Facebook friend, begin typing their name and select them from the list that appears. If the person isn't your Facebook friend, type their email address.
4. Click Editor  to select a role from the dropdown menu.
5. Click Save and enter your password to confirm.

Depending on their settings, the person may receive a notification or an email when you give them a role.

Reference: https://www.facebook.com/help/187316341316631