I have had several FreePBX 16 installations for several years and the last time I tried to update the Lets Encrypt certificate, if would not update the certificate in the HTTPD service. I tried both certificate management in the GUI and fwconsole certificates several times including deleting the certificate and starting fresh. Both showed that the certificate was updated but the HTTPD service never used the new certificate. Nothing I tried worked, I found that the ssl.conf configuration file in the /etc/httpd/conf.d directory was not being updated. It pointed to a certificate in the /etc/httpd/pki directory which was not updated and had the old certificate. The new certificate was created in /etc/asterisk/keys/.
I only got the HTTPD service working with the new certificate by manually editing the ssl.conf configuration file to point to the certificate in /etc/asterisk/keys/.
This should not be necessary, something is not working correctly.