If you are trying to upgrade to pro or update billing with a new credit card and the system is not accepting it, there are a few reasons why this could be happening.
1. Your bank/credit card company blocked the payment due to it being flagged. In this scenario, you would have to reach out to your bank and approve this transaction through them. The transaction could be flagged because of it being a foreign transaction or due to extra security from the bank.
2. The card you are trying to pay with has insufficient funds. This happens with debit card especially so double-check that the card has enough to make a withdrawal from.
3. The card information isn't correct or up-to-date. Go over all the card information and make sure all the information is correct.
4. You are not the Billing Admin in your ManyChat account. You can check it under Settings > Users. There should be a tick near your name in the Billing column like in the screenshot below. If it's not there, ask the Billing Admin to grant you this role and then try upgrading the account again.
If these steps do not work, please contact the friendly Support team for further assistance!