3CX SSL certificate has expired

[Andy]

Follow these steps to renew your 3CX SSL certificate (assuming that the PBX in question is SP0 as the last contact with 3CX servers has been made from a 15.5 SP0 – In this case, the system must be updated to the latest service pack)
To force the update:

• If the version is lower than v15.5 SP2 skip this step:
  • Starting from v15.5 SP2, go in Settings / Parameters:
  • Set or Add TEMPORARY_SELF_SIGNED_CERTIFICATE_GENERATED and give it value of 1.
• Linux:
  • Log in via SSH.
  • Type: /usr/lib/3cxpbx/PbxConfigTool -renew-certificates
• Windows:
  • Go to Command Prompt.
  • Type: “C:\Program Files\3CX Phone System\Bin\PBXWizard\PbxConfigTool.exe” -renew-certificates
  • Press Enter and the result should look something like this:
    
    
  • Restart nginx just to be sure and the certificate should have been renewed (service nginx restart)

I got the instruction above official from 3CX Support Helpdesk.