A bit of a lengthy explanation for a problem that Support has not come up with a solution for, and I’m going in circles.
I have two Drobos, generation 1 and 2 (referred to here as Drobo1 and Drobo2). Both were in use on a Win XP 32 bit computer, then moved to a Win 7 54 bit and both worked fine, retaining old volume names and being assigned new drive letters.
I upgraded 2 HDD in Drobo2, moving one into Drobo1 to upgrade that. I also wished to reformat Drobo2 into a single, 16Tb volume so followed the instructions to remove all data before proceeding. The result was, however, that Drobo2 recognises all four HDD (four green lights) and Dashboard states there is a single volume, but it fails to format this because it cannot obtain a drive letter. There are eight free letters and (as a test) adding other external drives or adding a network drive work fine, with new letters being used and released as required.
The increased size of Drobo1 means it wants a new volume created; this fails for the same reason, though the original two volumes (with their data) remain accessible with drive letters assigned.
Moving Drobo2 to the old XP computer and using Dashboard to erase and format as 3 2Tb volumes works fine. Putting it back onto Win 7 produces … nothing; Dashboard sees that there are three volumes, but no drive letters are assigned and no use can be made of the Drobo (which remember, used to be usable until switching a drive). New USB cable has no result.
Any ideas of what to try next are welcome.