@semarie I'll try to investigate to help you.
Is it possible to run:
stat /etc/xensource/xapi-pool-tls.pem
openssl x509 -in /etc/xensource/xapi-pool-tls.pem -noout -text
stat /etc/xensource/xapi-ssl.pem
openssl x509 -in /etc/xensource/xapi-ssl.pem -noout -text
(This file must exist; if not, I'd like the output of cat /etc/stunnel/xapi.conf.)
And I'd like the same output for /etc/xensource/xapi-ssl.pem.
If the certificate for /etc/xensource/xapi-pool.tls.pem has expired or it's empty, you can run:
xe host-refresh-server-certificate host=$(hostname)
If the certificate for /etc/xensource/xapi-ssl.pem has expired or it's empty, you can run:
xe host-emergency-reset-server-certificate
After running one of the two commands above, I recommend to do: xe-toolstack-restart
(This should indeed restart the stunnel@xapi.service)
I hope this helps.