I have a similar issue since I’m using Openhab 4.1.0 - my COAP communication seems to fail.
I’ve been succesfully using coap events for a long time, but it stopped working. I did not change anything on shelly side.
Tested telnet serverip 5683 which was not succesful.
(I would exclude that this is a firewall issue, tried local on server and with disbled firewall. port 8080 in cross check worked fine)
I realized that in shelly manager all message count is 0 - I didn’t not have attention to this number in the past, but looks suspicous to me.
To me it looks like me coap endpoint within shelly binding is not working correctly.
Any help or idea is appreciated