Google Wallet API通用卡创建失败：报错排查求助

我正按照Google Wallet通用卡Web开发指南配置Google Wallet Pass通用卡，已生成JWT负载，但在Google Wallet中测试时持续报错（截图：）。解码后的JWT内容如下：

{
  "iss": "xxxxx@xxxx.iam.gserviceaccount.com",
  "aud": "google",
  "origins": [
    "www.xxx.com"
  ],
  "typ": "savetowallet",
  "payload": {
    "genericClasses": [
      {
        "id": "<issuer_id>.<random_text>",
        "classTemplateInfo": {
          "cardTemplateOverride": {
            "cardRowTemplateInfos": [
              {
                "twoItems": {
                  "startItem": {
                    "firstValue": {
                      "fields": [
                        {
                          "fieldPath": "object.textModulesData['purchased_lattes']"
                        }
                      ]
                    }
                  },
                  "endItem": {
                    "firstValue": {
                      "fields": [
                        {
                          "fieldPath": "object.textModulesData['remaining_lattes']"
                        }
                      ]
                    }
                  }
                }
              },
              {
                "twoItems": {
                  "startItem": {
                    "firstValue": {
                      "fields": [
                        {
                          "fieldPath": "object.textModulesData['available_lattes']"
                        }
                      ]
                    }
                  },
                  "endItem": {
                    "firstValue": {
                      "fields": [
                        {
                          "fieldPath": "object.textModulesData['free_lattes_received']"
                        }
                      ]
                    }
                  }
                }
              }
            ]
          }
        }
      }
    ],
    "genericObjects": [
      {
        "id": "<issuer_id>.a372e87e-4347-4e7b-b326-f2e7fb649367",
        "classId": "<issuer_id>.<same_random_text>",
        "logo": {
          "sourceUri": {
            "uri": "<png_url>"
          },
          "contentDescription": {
            "defaultValue": {
              "language": "en",
              "value": ""
            }
          }
        },
        "cardTitle": {
          "defaultValue": {
            "language": "en",
            "value": "xxxx"
          }
        },
        "subheader": {
          "defaultValue": {
            "language": "en",
            "value": "xxxxx"
          }
        },
        "header": {
          "defaultValue": {
            "language": "en",
            "value": "xxxx"
          }
        },
        "textModulesData": [
          {
            "id": "purchased_lattes",
            "header": "Purchased Lattes",
            "body": "0"
          },
          {
            "id": "remaining_lattes",
            "header": "Remaining Lattes",
            "body": "5"
          },
          {
            "id": "available_lattes",
            "header": "Available Lattes",
            "body": "0"
          },
          {
            "id": "free_lattes_received",
            "header": "Free Lattes Received!",
            "body": "0"
          }
        ],
        "barcode": {
          "type": "QR_CODE",
          "value": "<some_url>",
          "alternateText": "a372e87e-4347-4e7b-b"
        },
        "hexBackgroundColor": "#0d7787",
        "heroImage": {
          "sourceUri": {
            "uri": "<some_url>"
          },
          "contentDescription": {
            "defaultValue": {
              "language": "en",
              "value": "HERO_IMAGE_DESCRIPTION"
            }
          }
        }
      }
    ]
  },
  "iat": 1680012899
}

已联系Google Wallet官方支持但未获有效反馈，使用平台「Validate」功能验证也无具体错误提示，恳请协助排查问题。

内容的提问来源于stack exchange，提问作者Alk