Error: Violations for metadata: [expiryTime should be at least 5 minutes in the future and no more than 24 hours after the current time
I found the error. It was a bug in my code. I was sending the incorrect date, the message timestamp was wrongly sent in the past, and the same happened with the expiryTime. So the error sent back by Amazon was correct.
I wrote a skill for alexa using the proactive notification function from Amazon. 
It was working fine until yesterday, I could see the amazon echo blinking with yellow color. 
When I queried the device "Alexa, check my notifications", the information was available.
However today it does not work and I get the following error:
"Violations for metadata: [expiryTime should be at least 5 minutes in the future and no more than 24 hours after the current time"
This is the notification I am sending, I include the current time and the expiration time with an offset of 10 minutes. See the example below
Any idea what could be wrong?
Thanks in advance,
Ester
{ "timestamp": "2019-01-30T00:11:20", "referenceId": "98871463", "expiryTime": "2019-01-30T00:11:30", "event": { "name": "Alerted", "payload": { "type": "AMAZON.MessageGroup.Alerted", "messageState": { "type": "AMAZON.MessageState", "status": "UNREAD", "freshness": "NEW" }, "message": { "type": "AMAZON.Message", "creator": { "type": "AMAZON.Person", "name": "eve" }, "count": 1, "urgency": "URGENT" } } }, "relevantAudience": { "type": "Multicast", "payload": { } } }