Normally, if the timeout is reached (120 seconds in your case), the GET call will return the records collected in that time along with a pagination link. If there were any quota reports on that volume, you would at least get some in that 120 seconds. So, it's surprising to me that you got 0 records. Is it possible that the query you provided is not returning anything? Could you try doing a GET on /api/storage/quota/reports/{volume.uuid} and see if you get any records?