Facebook:do not have permission to install tabs

This page does not have permission to install the custom tab.

I don't know what is wrong but been publishing videos and all that now I want to add calendar and it's not letting me??????

Can you give us your the formID you're working on? To clarify, you cannot add a calendar to your Facebook tabs?

Please give us more information regarding your question, so that we can assist you better.

Thank you.