1. It is not possible to use Google Pay within the sandbox;

  2. 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

  3. 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.