ERR_CERT_DATE_INVALID or 3CX expired cert

Before doing the procedure below, make sure to take a backup of your settings!

Go in advanced / Parameters:

Set or Add TEMPORARY_SELF_SIGNED_CERTIFICATE_GENERATED and give it value of 1
Linux:
- Log in via SSH and edit the file /etc/resolv.conf, leave only as nameserver 1.1.1.1 and nameserver 8.8.8.8 and save the file
- su phonesystem
- /usr/lib/3cxpbx/PbxConfigTool -renew-certificates
Press Enter and the result should look something like this:

Restart nginx. For Linux, to restart nginx type: service nginx restart