The "Online payments are currently unavailable" error means the property's default bank account does not have an active merchant account set up on it.
How to Fix It
Check if the property has a merchant account — Go to Settings > Merchant Account and confirm the account is active. If not, set up a merchant account first.
Verify the correct bank is assigned to the property — If the property is using a bank account without a merchant account, reassign the correct one at the company level or property level.