Hey,
im sorry, my english is not that good - but I really need help.
I bought the Anki App for iOS a while ago, but it doesnt sync.
Neither with my Windows PC nor between iPad and iPhone…
Of course I’m logged in everywhere with the same account and klicked “sync” …
I would be really happy, if you’d have an answer.
Thanks!
When you say “Anki App”, do you mean this one: AnkiApp Flashcards on the App Store
The IOS Anki app is called AnkiMobile and is the only one that isn’t free for vairous reasons explained here: Why does AnkiMobile cost more than a typical mobile app? / Anki Ecosystem / Knowledge Base - AnkiMobile/AnkiWeb Support
oh sorry - no, I meant the AnkiMobile App 
It’s okay. It is an app and it’s Anki, so you weren’t wrong.
As for your problem, what exactly was the result of syncing? Did it give an error or say it finished syncing despite showing an empty default deck?
Since all syncing goes to the Ankiweb servers, it may be helpful to log in to https://ankiweb.net/ to see what cards/decks are there.