Replacing JBOD drive in ReadyNas Duo v2

I use my ReadyNAS Duo v2 as my backup drive so I don't need a RAID. I set up my NAS with a JBOD with one volume per disk 1 = C and Disk 2= D. Both disks were 3TB

When disk 2  - D volume failed C was still up and running. I bought a new 4TB drive and plugged it in expecting it to auto configure as volume D again as the FULL 4 TB. I was OK with losing the backup data as it was just a backup for my computers. 

The RAIDar (4.3.8) shows the 2nd disk as green. When I clicked "setup" it takes me to the web based GUI (which is aweful btw) and the website has a tiny pop-up at the bottom that says "new disk detected. If multiple disks have been added they will be processed one at a time. Do not remove any added disk during this time"

Then after leaving it for an hour the RAIDar is showing the NAS as "booting" and the drive appears as ONLY 3TB in the Software. 

So so does that mean I spent an extra $80 for nothing? How do I expand that volume?

This software is absolutely dreadful because it tells you nothing about what is happening. I am a senior computer software engineer and I will never buy a Netgear again unless they do something to allow you to configure raid without doing a factory reset, create multiple volumes on one disk and format volumes.