Thats why you need to store the state which is the last read position as stated here: https://developer.adobe.com/app-builder/docs/resources/journaling-events/lesson2/ 

Alternate I could think is, create as non-web-action using alarm. And cron trigger the action every say 5 mins. Is this correct that "Reading journal events must be created as non-web-action using alarm cron?" This is correct.It can be a web action too using an alarm.Please refer to https://develope...

can you please share the request id? 

That would mean there are no new events. 

Once you set latest=true, in the response headers, you will find the link to the next position from where you need to start reading the latest events.  more details can be found here: https://www.adobe.io/events/docs/guides/api/journaling_api/#consuming-the-most-recent-events