Hello Charmaine .
the best thing to do is to make the checkout yourself make sure you enable the test mode for payment and test it :)
if that not working check your Abandoned checkouts and look for the customer who contacted you order from there you can see why the checkout was Abandoned some times that can be from your customer bank provider check all this things and try again :)
Hope That Help You if not Please Contact support team :
Email : email@example.com