Backstage - Azure integration - Stack Overflow

I try to interface Backstage with Azure,

Auth is working and I can register yaml files from ado servers, but discovery does not work

providers:
    azureDevOps:
      provider1:
        host: dev.azure
        organization: OurCompany
        project: '*' 
        schedule: # optional; same options as in SchedulerServiceTaskScheduleDefinition
          # supports cron, ISO duration, "human duration" as used in code
          frequency: { minutes: 1 }
          # supports ISO duration, "human duration" as used in code
          timeout: { minutes: 3 }
      provider2:
       host: our_server
        organization: OurCompany
        project: '*' 
        schedule: # optional; same options as in SchedulerServiceTaskScheduleDefinition
          # supports cron, ISO duration, "human duration" as used in code
          frequency: { minutes: 1 }
          # supports ISO duration, "human duration" as used in code
          timeout: { minutes: 3 }

I can access dev.azure/OurCompany and ouserver/OurCompany in my web browser but running backstage locally :

provider1 gives a 404

catalog error AzureDevOpsEntityProvider:provider1 refresh failed, Error: Azure DevOps search failed with response status 404 Azure DevOps search failed with response status 404 target=AzureDevOpsEntityProvider:provider1 class=AzureDevOpsEntityProvider taskId=AzureDevOpsEntityProvider:provider1:refresh taskInstanceId=ddbe593a-9053-45eb-b1f9-09b17764c720 stack=Error: Azure DevOps search failed with response status 404

provider2 returns a 505

 catalog error AzureDevOpsEntityProvider:provider2 refresh failed, Error: Azure DevOps search failed with response status 500 Azure DevOps search failed with response status 500 target=AzureDevOpsEntityProvider:provider2 class=AzureDevOpsEntityProvider taskId=AzureDevOpsEntityProvider:provider2:refresh taskInstanceId=7eb6bece-e1bf-4906-a58a-6ad5beaeb628 stack=Error: Azure DevOps search failed with response status 500

How could I debug this and figure what URL are used ?

Thanks for your help