Critical state - second drive failed while rebuilding drive. Help!

I was swapping one of the 5 drives ( was warned that the drive was failing) with the 5D3 when halfway through, it seemed that another drive failed. As a result I ended up with a warning that too many drives have been removed. I tried slot flushing and even tried root level cloning one of the two 4TB drives (4tb to 6tb) but the drobo does not recognise the cloned drive. One of the drives is making noises when I place into another computer to check so that’s probably failed.
The current 5 drives consisted of 3x 3TB, 2x 4TB. Prior to this I was using 5x 2TB drives in the same drobo which I have not erased. I tried inserting these 5 older drives in but the ‘too many drives message removed’ message persists.

How can I retrieve my data? Either the current drives or the previous set of drives. Do I have to insert these previous 5 drives into another Drobo?

A suggested pathway:
Obtain 2 HDDs (small capacity best) that have not been used in any of your Drobo Arrays to date.
Turn off your Drobo (even remove the power) and then extract you current array.
Insert the 2 new HDDs, reconnect and turn on the Drobo - it should start to reformat them as a new volume - confirm you have visibility and access to the new volume on your PC/Mac.
Shutdown and turn off the Drobo and then remove the 2 HDDs, and replace them with your previous 5x 2TB array - hopefully in the same order you extracted them some time ago.
Restart, and look for your previous volume to appear.
Assuming it does and you can access your date, make an external backup of your data.