I know from a friend, who has a restaurant and uses Qerko, there are some problems with ordering through app but are you sure not even payments were working?
Discussion
They apparently didn't link the table order to the table in the app. And they directly said that it would not work through Qerko. I am talking about the restaurant Kolkovna Argentinska
I already ordered through app and paid with lightning in two other restaurants. But the other two restaurants had qr codes on the tables and were on the Qerko map, but clearly did not want to work with the application and pay through it: CMKarting and Kolkovna Argentinska
The ordering and payment process looks funny: you come, you refuse the waiter, then they bring you what you ordered in the app, then you pay with a tip via lightning and you can leave. I also give lightning gift cards in Czech language (LNinv.com - my patched for czech language the tipcards.io server) - but they don't even realize that money is waiting (sats) for them on paper.
LNinv.com - Tam jsem si udělal překlad do češtiny pomocí elektronického tlumočníka a sám jsem si to ověřil (česky trochu vím). Pokud budete mít chuť upravit text-mám GitHub opravenou verzi - https://github.com/Perlover/tip-cards
Please look in DM of Nostr ;-)