This looks more like a Converter source-volume discovery issue than a cPanel issue itself. Converter can see /dev/vda2, but it’s failing to correctly associate the LVM logical volume /dev/rl/root with its underlying disk.
The large number of CloudLinux CageFS bind mounts on rl-root may also be confusing Converter's Linux volume discovery.
First, verify the LVM mapping:
pvs -o+devices
vgs
lvs -a -o+devices
lsblk -f
findmnt /
Confirm that rl-root, rl-home, and rl-swap all map cleanly back to /dev/vda2.
Before retrying the conversion, temporarily disable CageFS if possible and unmount its CageFS mounts, then confirm with mount/findmnt that /dev/rl/root has only the expected filesystem mounts. This helps determine whether CageFS is interfering with Converter's source discovery.
Also check that the source disk isn't using device-mapper multipathing, since VMware Converter doesn't support Linux volumes mounted through Device Mapper multipath. This is a limitation for Linux P2V conversions.
If the error remains after simplifying the mount layout, collect the Converter logs and check the entries immediately before No volume for partition /dev/vda2. At that point, it may be a Converter compatibility/volume-discovery limitation with this particular CloudLinux/LVM configuration rather than an LVM problem on the server itself.