First of all, make sure, that you have correct settings in Your Facebook app setup. To check it, go to: https://developers.facebook.com/apps

1. on the left side choose You app
2. than on the top right click on “Edit App” button
3. On the left should be choosen: Settings -> Basic
4. Go down into the section called: “Select how your app integrates with Facebook”
5. Find setup for Page Tab and check if you have set correct width of used app layout (mine was 520px)
6. Save changes, if anything changed
7. Than on the left choose Settings -> Advanced
8. In the section “Canvas Settings” should be following setup for canvas height: fluid