Webinar API always return 429 error

When our web app calls Webinar API, https://api.zoom.us/v2/webinars/ to register attendees, always return 429 error, too many requests. We have Zoom pro plan. So for light APIs, we should be fine if our requests is less than 30requests/second. Our multiple zoom meeting accounts and one webinar account have the same account owner and use the same account number. Will this setting effect the request limit? Does each account have their own request limit? Where can I check those information? Can anyone help? Thanks.