How to report app developer to Apple? I bought 1Blocker app for my Mac and iOS devices.

While it works on Mac and iPhone, the app is not functioning on iPad.

The developers on the app stated on their website that to get support, use Twitter.

I contacted them three times by now and they aren’t replying. I want to report those developers to Apple due their lack of support and misleading statement.

How to report them to Apple?
You will have an email invoice from Apple for the purchase. That email contains a "Report a Problem" link. But you can only report problems within 90 days of purchase.