3TB drive capacity limited

was it initialized before you upgraded to 4.2.19? Although I would expect the pro 6 to come with a firmware that supported 3tb+, and it looks like it see's the whole 2794gb.

is this the only drive in the device?

you may need to factory reset one more time

If you don't have any data on the Pro 6, try a factory default. It appears as if it is not using GPID partioning on the drive. It appears the Pro 6 shipped with 4.2.15 or earlier and you upgraded to the newest version (4.2.19) after the volume was established.

Yes, this is the only drive in the device.
When I got the device, it alerted me immediately to upgrade to 4.2.19
It does see the whole disk but from some reason only allocates a small portion of it.

Ok, you got the NAS and set it up and then got the message to upgrade to 4.2.19. Did you perform a factory default after that point?

If not, and there is no critical/important data on the NAS, perform a factory default as follows:

Ultra 6 / Ultra 6 Plus / Pro 6

To access the boot menu:

Power off your unit.
Using a straightened paper clip, press and hold the Reset button.
Press the Power button to power on the unit.
Continue to press the Reset button until the status display screen shows an boot menu message.
Press the Backup button to scroll through the boot mode options.
Press and release Reset button to confirm your boot menu selection.

The system boots in the selected boot mode.

With only a single drive it should take about 15-20 minutes to reformat the drive and establish the volume. (Note: it is the multi-drive synchronization that take the time, measured in hours).

Thank you, this worked wonderfully!

You are very welcome. Enjoy your unit.