I followed the migration steps, ensuring that both units were updated to the latest firmware. Dashboard informed me that both devices were already running the latest firmware. I was careful to connect the data cable to the 5N before connecting power.
I used Dashboard to shut down the FS. I tried to shut down the 5N using Dashboard as well but it just sat there spinning forever. The (empty) Drobo 5N had all drive bay lights red and was flashing all the blue LEDs and the right-most LED. It wouldn’t shut down so I used the switch on the back.
I moved the drives over from the FS to the 5N (three 3TB drvives, one 4TB drive) and then powered up the 5N. It started booting normally. Soon, the drive bay lights came on and turned yellow. However, when it started “counting” blue LEDs during startup, it got to about the fifth blue LED and then instantly changed to all RED drive lights and started flashing all blue LEDs and the right-most green LED.
Dashboard can’t see it. Rebooting the 5N using its power switch results in the same outcome every time (red drive lights, flashing blue LEDs, forever).
I saw a web page somewhere that I can’t seem to find any more that mentioned which model Drobos can be migrated and which can’t (The support info only talks about which “gen” the Drobo is; how am I supposed to know that?). Anyway, my Drobo-FS model is DRDS2-A. The 5N is brand new.
Any help with this would be immensely appreciated. 
P.S. If there is a problem with my 5N, is it safe to move the drives back into the FS? I am expecting not. I do really need my network storage back as soon as possible.