Add HDD to RAID5

I see a lot of people have asked this and don’t really get an answer.

I had 3 x 4TB WD Red drives in my device configured with RAID5. I now put a fouth 4TD WD Red HDD in the enclosure and want to know how to add it to the RAID without having to backup data fromt he device to an external source and then create a new RAID and start from scratch. The website says you can add to a RAID array but I can not see where there is the option of adding a disc to the RAID and the answer given on this board by WD seems to be “The RAID will automatically rebuild” but after several resets and a lot of time waiting I am yet to see the device even contemplate adding the new disc to my existing RAID5.

What is the process required?

Be sure to enable the auto rebuild option from the EX4 dashboard. Check page 72 for more information.

It is ticked and has been since first setting up the device two months ago. Yet still it does nothing to initiate extending the RAID to include the new drive. Just wondering - have you used any of the devices in the context you are giving advice on?