Hello,
Converter does not reconfigure Linux machines in case of powered off conversions (by design). Since Hyper-V has a different virtual hardware, it is expected that the destination is unable to boot.
Redo the conversion as P2V (the easier way) or do a manual reconfiguration of the converted VM. E.g. powered on from a live CD, install GRUB (recreating the grub.cfg might be needed) run dracut, check fstab and network configuration files.
HTH,
Plamen