Faced with a problem: when set the automatic payment method, on the shopping cart page, still shows: "payment method is not selected - select payment method", the version of virtuemart 2.0.24, solution:
1. open your_site file/components/com_virtuemart/helpers/cart.php
2. then find there function: CheckAutomaticSelectedPayment, line 1220
3. in this function, we find the condition: if (isset ($ returnValue)) and change it to if ($ returnValue == true), line 1232
I helped.
You should not need to change any code!