Hi @GhezziA
checking your port - https://check-your-website.server-daten.de/?q=sip.eservizi.it%3A5061 - your installed certificate is revoked.
Revoked: The certificate is revoked.
And it sends the intermediate certificate that uses the
CN=ISRG Root X1, O=Internet Security Research Group, C=US
04.06.2015
04.06.2035
expires in 5336 days
That's good. But it's unknown if the error message happens because your certificate is revoked (so the error message may be not so good).
So: Hitting the limit -> wait, then create one new certificate, then install it.
And check, if the ISRG root is installed.
PS: The warning isn't so really relevant. It's more a client warning. If an older Windows client tries to connect your server, that may fail.
But your server doesn't send the root certificate (that's good), so it's not really a server problem.
It's a warning, not an error.