hi ok no worries.
as far as i could tell, it sounded like you had it working before, and 1 drive failed, and that powered it off and then replaced the bad drive and powered it back on and had the problems as above?
if so, then the idea behind it is to try this as it might help:
eg. to power all off and get it back to how it was eg with the original drives inside, (eg to put the bad one back in)
and connect it to the computer
and then power up the drobo and let it boot up (and probably go into standby mode)
and then power up the computer and let it boot up
does the drobo now wake up shortly after, and is it shown on dashboard?
(if dashboard says too many drives removed, then you might need to power all off again, and then to put back in the replaced drive and to then power back up to see)
it may be the case that it confused the drobo when you tried to replace with power off, as usually the unit should be left on, and faulty drive removed, and then the replacement put back in all while still running etc.
btw when you went to replace a bad drive as you mentioned, can i check how you knew it was bad? (eg was dashboard saying things, or was drobo flashing lights at you etc?)