Hello,
01. Install the free Storefront theme from WordPress > Go to Appearance > Themes > Add New > Search for Storefront, install and activate it > Test the checkout process with a product and payment.
If the payment works correctly with Storefront, then the issue is likely related to our theme. If it still shows “Processing,” the issue is probably with the payment gateway or WooCommerce settings.
02. This color in the WooCommerce checkout error messages is coming from the Warning Notice Background Color setting. You can change it by navigating to: Theme Settings > Styles and Colors > Notices > Warning Notice Background Color: https://ibb.co/fVd0Cb15
Best Regards,