There are two cases when your page's Pro subscription switches back to Free:
1. You've canceled your Pro subscription at some point and it has expired at the end of the billing cycle eventually.
If you wish to re-upgrade the page, please click the 'Renew Subscription' button in Settings => Billing and then follow instructions from the system:
2. The system wasn't able to charge your credit card at the end of the billing cycle due to a certain payment error ('insufficient funds' or 'transaction blocked by the bank', for example), and your Pro subscription has expired as a result.
As soon as the system indicates a problem, it will start sending automatic notifications that there was a failed payment attempt: if the issue still persists after the 4th notification from the system, your subscription will expire.
First of all, you have to make sure your credit card has sufficient funds on it to allow the system charge it successfully.
If that's the case, you'll need to contact your bank and ask if it declines this particular operation for some reason - hopefully they'll be able to provide the necessary assistance to solve the issue.
If you wish to re-upgrade the page using different credit card or change the billing e-mail, head to Settings => Billing and click 'Update Billing Credentials' button here and follow instructions from the system:
Please note: while the subscription gets Expired, it's not getting cancelled if you don't do it manually on your side, which means that if the system manages to charge your card eventually, your Pro subscription gets renewed automatically. If you want your page to remain on a Free plan and stop receiving automatic notification from the system about failed payments, please click 'Cancel Subscription' button that you can see on the screenshot above.
In case there are still any questions left - feel free to submit a new ticket to our Support Team at any moment!