PayPal Standard payment method stopped displaying in cart.

Just completed what appeared to be a successful upgrade from 2.x to 3.x except for an issue with the PayPal Standard Payment method extension. The PayPal method was displaying at Checkout then stopped displaying. When it was displayed there was a problem re-directing to PayPal when the button was clicked at the end of the Checkout page ("Things don't appear to be working at the moment. Please try again later."). Now I am unable to get the method option to display at all. I can get other payment method options to display, but we do not want those. We only want PayPal. I can enable the PayPal Express extension and the button displays and works. However, the checkout process still requires at least one payment option for selection during checkout. Anyone experience this before and solved the issue? Any advice on how proceed? I uninstalled / installed the PayPal Standard extension, made sure it was configured correctly, checked currency (using US), etc.. Thank you.

I ran into this as well. Make sure you re-enable the correct Order Totals extensions. PayPal will give that error if you are missing required fields such as order total and such.

Thanks. This helped!