I created an Ubuntu 18 workstation VM using Virtualbox 5.23 on my local workstation ("MYSELF"). The VM runs beautifully.
When I transfer the folder of the VM to another workstation ("COLLEAGUE"), adjust the ownership for my colleague's username and group, add it to the Virtualbox 4.3.40 on COLLEAGUE, check to make sure all settings reflect the local machine's paths (though they are identical on both our machines since we put VMs into: /usr/local/virtualbox/ which has the permissions set to allow rwx for the main user of the machine), then hit START, it very briefly flashes the purple Ubuntu screen and then goes black with just a cursor in the upper-left corner.
I have also tried TARing the folder and moving that over, to no avail.
Also, Virtualbox Guest additions and the Virtualbox Extension Pack have already been installed on COLLEAGUE.
Both host machines (MYSELF & COLLEAGUE) are running Ubuntu 14.04.5 (Yes I know, we are in the midst of upgrading, hence running some tests with Ubuntu 18 in Virtualbox).
When I try to ping the VM (it was given a static IP), no response.