Problem

No payment methods available at checkout.

Solution

First of all please check your enabled payment methods settings in Admin → Extensions → Payments

Total Order Minimum/Maximum - values should be empty to allow any order amount to checkout with your Payment
Payment Location setting - please set it to 'All Locations', in case you need to limit Payment checkout for some location - make sure your customer address is within selected Location.
Check all your Shipping methods installed because every shipping methods have 'Allowed payments' settings - if you limit your shipping methods to work only with selected payments this can be a reason why your payment method not shown at checkout.
And the last one - please check your AbanteCart error log (Admin → System → Logs) for the payment related errors.