Unable to save file to cloud - button appears grey

Just this morning I was trying to save a document (5x7 in.) to Creative Cloud, except when clicking the "save" button the "Save to cloud documents" button was unclickable and grey. This has never occured before. I cleared my Preferences last evening because of another issue (now fixed), if that might affect anything. I'm on the latest version of Photoshop, 25.6.