In my experience, such continual connect/disconnect is caused by a duplicate MQTT client ID.
on V 3.1.1
on V 5
So it is likely that the broker does not support it.
I left the client id blank for automatic generation
should she be a constant to everyone ?
I have had the problem for over 2 months now, during this time I have also tried to search for the problem on my own by which I came across your earlier posts and also tried to follow them but unfortunately nothing helped.
only thing is that earlier I had "keep alive" set to 45 after changing it to 60 the occurrence changed from 4-5 days to a week- two weeks without any problem.
I really appreciate your time 
I am confused. You said two hours ago that it fails every 4-5 days, now you say that since you made that change it has worked for two weeks without a problem. Please clarify.
at the very loss I wrote in brackets (once every 4 days, every 5 days, the last 2 weeks)
two weeks it worked after changing the "keep alive" to 60 from 45 but this could just be a coincidence
I am sorry if I have misled you
No, should be different for every connection - left blank should do that anyway.
According to AWS IoT Core docs, it does support many (not all) V5 features: MQTT - AWS IoT Core
But it should connect. You should try again (perhaps restart node-red changing just in case).
V5 has a lot of benefits, and in this case, v5 has greatly improved status info & so your logs should include reason codes (and if AWS did a good job, you should also get a friendly reason description alongside the reason code)
Did you try to monitor the topic $aws/events/presence/# ? There you will find disconnection codes that may give you some hint.
Reference: Lifecycle events - AWS IoT Core
I found something like this
(node:29) Warning: Setting the NODE_TLS_REJECT_UNAUTHORIZED environment variable to '0' makes TLS connections and HTTPS requests insecure by disabling certificate verification. (Use `node --trace-warnings ...` to show where the warning was created)
Hi
After 20 days
all MQTT discconected
in logs typical
"connected
disconnected..."
as above
