GraphAPI: Search External Item return 500 for the new created Connection

Reproduce step:

1. Add a ServiceNow Ticket or Knowlege connection from https://admin.microsoft.com/adminportal?#/MicrosoftSearch/Connectors.
2. Use basic authentication type and select Everyone for Access Permission. Leave other as default, and proceed with creating the connection
3. Wait until the connection state to be "Ready"
4. Go to https://developer.microsoft.com/en-us/graph/graph-explorer, search for external item, select search external item
5. Update the contentSources in the body with the created connection id, and run Query

Expected: the search return 200
Obtained: The search retun 500 error. It will go back to normal state in 15 or 20 minutes after the source is indicated as "Ready"

Sorry for posting this in the wrong place but I could find Azure Active Directory App Integration and Development with the below instruction. Please help me put this in the right place give me the updated instruction

1. Open https://portal.azure.com/#create/Microsoft.Support
2. From the Issue type field, select Technical.
3. Select your subscription from the Subscription field.
4. From the Service field, select the Azure Active Directory App Integration and Development field.
5. Enter a summary in the Summary field.
6. Select GraphAPI from the Problem type field.
7. From the Problem subtype field, select the subtype the most closely fits the issue you encountered.
8. Select Next at the bottom of the field and follow the instructions.

Start by reproducing the request in Microsoft Graph Explorer with a newly created ServiceNow Ticket or Knowledge connection, following the listed Azure portal steps. No repository file or test is named; done would require identifying the responsible component and confirming that searching the external item returns HTTP 200 immediately after the connection reaches Ready.