Hello Franco,
Just to mention that the distro you want to convert, freepbx, is not supported by Converter. By which I mean it has never been tried and is expected not to work (nothing is officially supported anymore now that Converter is EOL).
In such cases the recommended course of action is to boot the converted VM from a live installation ISO image and do some manual reconfiguration job. Since freepbx is a Red Hat derivative, Converter has probably made some right guesses. E.g. it seems GRUB has been installed correctly. Converter has detected dracut as initramfs maker. You should check whether this is correct and you should certainly recreate the initramfs image from the live boot. You may want to also check fstab patching (do this before recreating initramfs).
You may have a look at these threads for more details about manual reconfiguration of converted Linux machines:
Re: Conversion fails with the error:FAILED: An error occurred during the conversion:'root is not found'
Re: converting Linux server OpenSUSE 13.2 with kernel 3.16.7-29-desktop error : installGrub.sh failed with return code…
One more hint:
- There used to be an issue related to Red Hat starting to use '/run' system mount more actively (Converter doesn't mount it). Related to that, versions in the range 7.5 - 7.6 (approximately) were unconvertable. If that's the case, an eventual upgrade of the source might help. Keep in mind version 8 is unconvertable, though!
HTH
Plamen