Export and import of any virtual box machine from one PC to another is done simply by “File – Export Appliance” and “File – Import Appliance” in Oracle Virtual Box top menu.
But it happened to me that I exported and imported an Ubuntu machine and internet connection was not working in the imported appliance. After a long research and google searching I found a possible way how to fix it.
If you moved your OS from one machine to another it might be a good guess that udev created a configuration containing the MAC address of your old network device which is different from the MAC address of the network device from your new system.
Try removing the following file then reboot your system and see if this solves the problem: