In the previous post I wrote about finding the issue by doing a slot flush on each drive. When I reached the 4th drive the slot flush did not work, and the Drobo exhibited the same pattern I saw when attempting to boot it.
Having no other answers to what I was seeing I made the assumption that drive 4 was bad. I went to the store and bought an identical drive of same size and speed. With the Drobo powered off, I removed the old drive in slot 4 and inserted the new drive. I also verified that all 5 drives were securely locked in.
I powered on the Drobo and within a relatively short period of time was able to once again gain access to it through the Drobo Dashboard software. It showed me that Data Protection was running and estimated (way too high) how long until the new drive would be rebuilt.
I do have a 64GB m-SATA drive (accelerator) in the slot on the bottom of the Drobo 5N. I'm not sure if this made a difference but aside from what the Dashboard reported as the amount of time to for data protection to restore the new drive, the actual time ended up being about 11 hours. This is on a unit with a total of 20TB of drive space, and about 14.9TB usable. I had used 80% so this device was close to full. The Dashboard started off saying it would be 93 hours to restore. That estimate went down over time but still remained higher than the actual time.
I am not sure if the m-SATA helped speed things up, or if the fact I use 7200RPM drives helped, but I wanted to let others know the restore can happen relatively quickly. I have read where other's have taken days.
I wanted to make sure nothing attempted to write to the device during the restore so I disabled anything I use that might have tried to write to the Drobo during the restore. One thing that is incredibly nice was I had access to my data during the restore process.
I hope this additional information answers some questions others may have if they go through the same experience I did.