The "Quick Export as JPG" option no longer works - from either the contextual menu or the main menu bar.
UPDATE: For reasons I don't understand, this is working now. I opened up an old PSD file that I built before updating to 2017 and the export featured worked perfectly. So I tried it on a few others, including new ones built with 2017 and the export feature is now working on all files.
I get a similar issue with export as PNG. Works sporadically and then it stops. Rebooting Photoshop fixes the issue for a while then it goes back to not working. Running the latest version of CC on a fully updated Mac OS High Sierra but have experiencing this issue in previous versions of Photoshop as well.