PS error message after editing and trying to add back to Lightroom; what's happening?

Each time I edit my photo resolution to 300 or even 600, the first photo saves; however, every photo I attempt after that hangs with this error message and does not get added back to Lightroom.  I am using LR and then "editing in PS". Thanks for your help.  I am not the sharpest pencil in the box when understanding these things.