Finally had some time to look into this issue again, I don’t have a resolution but maybe some more info that may help.
This is the redirect url after clicking “Ok” when the Developer error appears.
To me it looks like a capacitor issue that doesn’t allow the google pay window to open as a popup hence not being able to read or atleast return data.
https://localhost/home#__WA_RES__=%7B%22requestId%22%3A%22GPAY%22%2C%22origin%22%3A%22https%3A%2F%2Fpay.google.com%22%2C%22code%22%3A%22failed%22%2C%22data%22%3A%22%7B%5C%22statusCode%5C%22%3A%5C%22DEVELOPER_ERROR%5C%22%2C%5C%22errorCode%5C%22%3A2%2C%5C%22statusMessage%5C%22%3A%5C%22Popup%20blocker%20detected%2C%20you%20must%20handle%20the%20clickEvent%20synchronously!%5C%22%7D%22%7D