Disk Utility

Did you select the physical drive in the left pane of Disk Utility when you erased it? If you only erased the pre-formatted volume, then it may cause issues on a Mac. To see the physical drive in the left pane of Disk Utility you need to click on "View" within Disk Utility and select "Show all devices". When erasing the drive select GUID partition and MacOS Extended (Journaled).

If this does not work, report back on what happened with this technique.

Try manually partitioning the drive using the Terminal command line. Try this one first:

diskutil  partitionDisk  /dev/diskN  GPT  JHFS+   VolumeName  R

If it does not work, then try this command:

diskutil  partitionDisk  /dev/diskN  GPT  JHFS+   VolumeName  99%

Replace the "N" in "/dev/diskN" with the proper drive ID for the external drive. In your screenshot this was "disk2", but check for the correct ID before running the command since the drive ID may be different each time the drive is connected.

The first command should use the entire drive, while the second command will only use 99%.

Try the last command again, but use 50% or even 25% instead of 99%. If it fails with a much smaller size partition, then either you have found a very odd bug in macOS or perhaps your new drive is defective in some way.

You could try running DriveDX (using the special USB driver to communicate with a USB drive) to see if you can get the health status of the external drive. Unfortunately many external USB drive's controllers do not allow the necessary SMART commands to be passed to the external drive. Might be worth a try to see if any blatant errors show up on your external drive. Even if DriveDX reports the drive as healthy, please post the DriveDX report here using the "Additional Text" icon which looks like a piece of paper.

You can also try writing zeroes to the entire drive to see if it is possible. Sometimes writing to a drive will force the drive to reallocate a defective sector which could "repair" the drive and make it functional again. Here is the command to write zeroes to the entire drive. Again replace the "N" with the correct drive identifier. The drive needs to be unmounted first (not ejected). Erasing a 6TB drive may take a day or two.

Unmount any and all volumes on the drive (replace "<volume-name>" with the actual volume name. If the volume name includes spaces, then enclose the volume name in double quotes " ".

diskutil  unmount  <volume-name>

example with a volume name containing spaces (Untitled 1):
diskutil  unmount  "Untitled 1"

Write zeroes to the whole drive:

sudo  dd  if=/dev/zero   of=/dev/diskN

Once the command finishes, make sure it wrote 6TB of data. Anything significantly less would mean you have a hardware issue with the new drive. You may need to do a little math.

If you are still within the return period, you may want to exchange this drive for another one. Otherwise try writing zeroes to the whole drive. If it works, great. If not, then you can create an RMA with Toshiba to get it replaced under warranty.

Do you have a powered USB3 hub you can use just in case the drive needs extra power and to have the hub act as a buffer between the drive and the computer? I've had intermittent issues using USB3 drives connected to a Mac and the powered hub makes everything just work.

While the report is limited, the report does mention 15 I/O Errors and 15 Read errors. I would suspect there is an issue with the drive. I would exchange or replace it.