Pre-processing script is not be able to get result from SearchIncidentsV2 command

[M.Wang287346]

Hi Community!

We're using XSOAR Version 6.0.

Our preprocessing script is not working as expected. 

We can't find exactly what causing this but we have a dev XSOAR instance and Prod XSOAR instance, the preprocessing script is working as expected in dev instance and finding the existing incident by the `SearchIncidentsV2` command successfully but it doesn't work in the prod instance. both XSOAR has same version and similar setup and I am sure the ticketnumber exist in production as well. The weird thing is when I manually trigger the 

`SearchIncidentsV2` command in playground in production, it did give me back what I am looking for. 

Before I am using `SearchIncidentsV2`, I tried `getIncidents` and `getIncidentbyQuery` neither works in either of the instance. 
This is dead simple query and I tried hard looking on internet but couldn't find any useful example that can help with identify where is wrong.

Here is the attached preprocessing script.

def main():
    incident = demisto.incidents()[0]
    ticket_number = incident.get('CustomFields', {}).get('ticketnumber')
    if ticket_number:
        query = f'ticketnumber:{ticket_number}'
        res = demisto.executeCommand('SearchIncidentsV2', {'query': query})
        if res and res[0].get('Contents', {}):
            return_results(False)
        return
    return_results(True)