Hi @Vjard
I encounter the same problem with the custom reports.
The solution is, you need to put your custom reports in Json Format.
Here is the correct Json Format. You can try
[{“name”: “AirbyteForum”,“dimensions”: [“date”,“deviceCategory”,“firstUserSource”,“firstUserMedium”],“metrics”: [“activeUsers”,“totalUsers”,“newUsers”,“sessions”,“transactions”,“totalRevenue”,“userEngagementDuration”,“screenPageViews”]}]