after hot swapping a dead drive, no volumes available? RN104

Hi all, 

I need a little help. I hope this is an easy one to fix here's the story so far:

ReadyNAS RN104, (system version 6.10.3) reported a failing drive, which then became a dead drive. The system had 4 3TB drives.

• Replaced the dead drive (the no.3 LED on the front of the head unit was off so the was the drive to change)
• I hot swapped the drive - replacing the 3TB drive with a brand new 4TB drive from the packet.
• Received an email from the system reporting that it recognised the new drive. It did NOT start syncing.
• There was a message in the main admin webpage telling me to remove the inactive drive to gain access to 1,2,4
• After over an hour, I did remove the new 4TB hard drive, but still no access to those remaining drives.

I'm tempted to turn the head unit off in the hopes to regain access after turning back on, but I really dont know what to do.

Not sure the best move. At the minute there is some legacy data, which will be important to save - so if I can regain access, I will be able to backup essential files.

I dont think the data has been deleted, but at this stage I dont know. The NAS system is aware of the volumes and I see them on my computer, but there is no access to whatever is inside them.

Has anyone had this situation and resolved it? 

Tried to get Netgear support but as the system is no longer supported I can't seem to get anywhere with them. That would be another approach to try, and if anyone has advice on approaching them, I would love to hear that also.

Thanks for your help in advance.

Aaron