Could it be that the thread you make the call on is not the thread you get the reply on? It sounds like it's there and returning to show on your main thread. Did you get this resolved? Just curious.

So I can confirm what swebal posted 6 days ago works. You get a very generic error for MacOS about 1024x1024 app icon missing even though it is in (Xcode 12) the Assets.xcassets folder as well as in the Preview Content -> Preview Assets.xcassets folder. I selected all of my images in the Preview Content assets package. Then did a copy. Then I selected the Assets.xcassets folder and did a paste. First time it gave me a bunch a AppIcon.1, Appicon.2 images which I deleted but it DID create the image sizes from the Preview Assets.xcassets folder. I then selected the map icons again as a group, did a copy and then went back into Assets.xcassets folder, selected the new Mac OS sized icons and did a paste. DONE. Then I also made sure the Attribute for this folder was set for BOTH iOS and MacOS. I was then able to submit for review with a SUCCESS. Thanks again to swebal for sharing this.

So I removed all of my foreign language tags on my app for iOS. Then I deleted all of the items in my Apple TV area. Then I filled out the boxes in tvOS App for the following: Promotional Text Keywords Support URL Description Until I STOPPED getting errors in the tvOS App area. Then I went and clicked on the iOS APP area again and hit save and it worked. Then I hit Submit for review and it WORKED! My guess is I had multiple instances of App Store Connect open for cut and paste and it threw it off? In short I just kept throwing mud against the wall until something stuck. It could very well be someone at Apple saw this post and fixed something on their side? No clue. Regardless I finally got this resolved but it's kind of confusing with a single APP bundle getting split three different ways for iOS App, macOS App and tvOS App. When the Universal App 2 comes into play it's going to get super simple.... lol. sarcasm.

With Mac or Linux you need the latest Gutenprint print drivers and have to build it for CUPS. You'll have to search for 'linuxfromscratch' and find their page about Gutenprint-5.3.3. The peachy photos link has details about drivers and that guy is a guru on the commands you can send, especially for DNP printers. Good luck!