Cannot transfer Catalog to external drive

I recently was on a trip and edited photos on my laptop and now that I am home I wanted to transfer them to my desktop.  I have gone to Export as Catalog and when it is about finished I get a notice "Lightroom was not able to export catalog because of an unexpected failure".  I have tried this a number of times with different external drives and even cables with no success.  Can anyone explain to me what this is about and what I can do to save the work I have done?