Storage Problems?

I am not being allowed to save photos I've edited because of "low disc space."  However, I've just recently started using lightroom, so my cloud storage is nowhere close to full, my computer's hard drive has space to work with, and I've tried saving to my external hard drive, which has PLENTY of space left.  Where exactly is the low storage space that they're talking about?  How do I free it up?  Does anyone have any idea what I'm talking about?