Lightroom and Photoshop no longer syncing

For some reason, my Lightroom and Photoshop are no longer talking with each other. If I try to use "Open in Photoshop" within Lightroom, I get an "Edit in  Photoshop" failed error.  And here's the thing: the photo actually does open in Photoshop .. but any edits are not saved back to Lightroom.

Any idea of what's going on?

Thanks!