Unless you see an error page that has error codes as such: “Error 100X”, then the issue lies with Google.
Only certain countries, at the moment, support Google Pay/Pass tickets. Please check if your country falls in the list by going to:
and click on “Make contactless payments, use loyalty cards, gift cards, offers, event tickets, and boarding passes” to find out if your country is supported.
Unfortunately, we cannot do much about it at the moment.