Custom tab not allowed on a page with more than 5 K followers

Hello, 

I cannot insert a Jot Form on a page, which has more than 2K followers. The message I receive is  This page does not have permission to install the custom tab.

What migh be the reason?

Apologies for the inconvenience, but I think this may be a common problem related to a bug or another restriction on facebook side. Please review the following link for more information: https://help.powr.io/hc/en-us/articles/360003062354-Facebook-This-page-does-not-have-permission-to-install-the-custom-tab-error