It is not possible to use Google Pay within the sandbox;
If you are getting an error 5.04, you need to check if the API keys are correct;
You can do it by going to HUB -> Developers -> Channels
Make sure that you are including the parameters
"geo_country"and"google_pay_merchant_id"within your PaymentIntent. So the list of obligatory parameters will be the following:
ip_address currency amount order_id order_description platform geo_country google_pay_merchant_id
Also, below, you can find links to instructions on how to connect Apple Pay when connecting via:
If none of the above helps, please contact Solidgate Customer Service and provide all the steps you checked and the error you encountered.