Maybe someone bought the old Ambrosia name, otherwise this developer/company has been around for a long time. Strange/sad that you can't make contact.
I do remember the name Andrew Welch! I think I may have tried their screen capture app, Snapz. There is a thread at Reddit, it's 2 years old with no recorded solution. Plus a different name is mentioned concerning "support". Sad that foul language always seems to be a problem at that site...
The info at Wikipedia says that the Ambrosia web site was closed down in July 2019. That probably explains why Safari says their server dropped the connection. These indie devs, even when they are successful, sometimes change what they do for a real living and can even cease 'production' or, worse yet, die!
I can only suggest you demand a more user-friendly response from Apple. Do you have Mr. Cook's email address? I think it's simply tim@apple.com or maybe timcook@...
Just noticed that the Copyright date on the app store stops at 2013... I generally question any site that doesn't keep that date up-to-date, assuming they even post the info. Certainly not encouraging when posted by a "dev". A very simple PHP script can update the year automagically on a web page.