Hi Desperate Recover, and welcome to the forum.
Your username says it all and I do sympathise. However I don't have a simple answer, and to hopefully get somewhere we need more info from you.
What was the reason for the need to recover data. Faulty drive? Accidental deletion? Accidental format?
What Operating System are you running?
The error message you are getting doesn't seem to have a definitive explanation from any amount of googling, although it usually means that for whatever reason the file system and/or the drive parameters are no longer able to be determined by the host computer.
Without having the drive in front of me I would hazard a guess that ...
a:) The ability to scan and recover with Recuva in the first instance may have been fortuitous and ...
b:) The reason it was fortuitous is that there is a problem with the drive which has manifested itself more seriously when a second scan was attempted.
What happens and what info is displayed when you now attach the drive to your computer?
a:) Does Windows assign a drive letter to it?
b:) In Disk Management, does it show up as having a recognised partition and file system, or does it now show up as "Unallocated Space", or in other words, as a "Raw" drive?
If you can provide as much info as you can, we'll have a look at the possibilities open to you. File recovery isn't an exact science sadly, and it isn't outside the bounds of possibility that if you unplug your drive and reattach it, Recuva might be able to access and scan it again.
Over to you squire, give us all the info you can.