hi patricia, welcome to the forum
from what you mention, it does seem to sound like the main unit has had a problem.
(usually, a good test is to do something similar to what you did, which is essentially to power all down, unplug cables, and then remove all of your diskpack drives, remembering the order for later, and then to try and power up the empty drobo, which should become recognised in dashboard)
however, if it is shutting down and booting up and basically reboot looping, without any drives, i think the problem could also be with the unit.
(if you happen to have access to another psu, or another compatible one for the 5d via the link below), then you could try another psu to see if just changing the psu and cable/brick etc, fixes the currently empty drobo doing the same thing:
though if it does not, a new unit is likely to be needed.
(aside from costing a fair bit more than a psu, it is almost always better to have a failing chassis, than a failing diskpack) i say this because when my drobo-s-gen2 had a power switch problem, i was able to follow the migration process below, and to successfully migrate my diskpack into a replacement unit, and access all my data again, for example as mentioned below:
(please remember though, that diskpack drives should only be removed, or inserted, in their entirety, and only when power is all off and cables unplugged)