Which Port to user to allow API Connection

My Software Setup
Main Website: WordPress + OptimizePress
Sub Domain : Mautic v4.4.10
My PHP version is : 8.0
My MySQL/MariaDB version is : 10.3.39-MariaDB
Web Host: Hostinger VPS + CyberPanel


  • I am using Hostinger VPS with CyberPanel
  • Using WordPress + OptimizePress on my main domain
  • Using Mautic on sub-domain
  • Trying to connect OptimizePress & Mautic using their API connector but not working

Steps I have tried to fix the problem :

  • One of the suggestions was to open ports #80 & #443 to allow connection between main domain & sub-domain
  • I added these ports in my CyberPanel as exceptions (to keep it open) but the API connection between WordPress (OptimizePress) & Mautic is not working
  • Is there any specific port that I have to open to make the API connection possible? How do I find it?

Any idea? Please suggest