When I try to "Quick Export as PNG" nothing happens, and when I try to "Export As" it times-out trying to load the dialog box. This happens more often for me with bigger files. Is there a file size limit where these functions stop working?
My workaround is Save for Web (legacy) which always works, but is a slower workflow.
We're sorry to hear about the "Quick Export as PNG" not working, could you please let us know which exact version of Photoshop you're working on? (You can find that out by going to Help > System Info).
Also, which operating system you're using?
I'm on Adobe Photoshop Version: 19.1.2 20180302.r.277 2018/03/02: 1160083 x64
Thanks for providing the information, could you please try updating Photoshop to version 19.1.3 via the Creative Cloud app and see if it helps?
If you do not see the update then please try signing out and signing back into the Creative Cloud app and click on the 3 dots on the top right corner and choose "Check for updates".