Developing on Thunkable X for iPads and iPhones

Hi all. I recently submitted my app to the App Store. One of the reasons that it was rejected was because Apple stated:
"We noticed that your universal app did not run or display as expected when viewed on iPad running iOS 12.0.1, and included overlapping content.

To resolve this issue, please revise your app to ensure it runs as expected and displays properly at iPhone resolution on iPad. Even if your app was developed specifically for iPhone, users should still be able to use your app on iPad. "

Has anyone actually managed to create an app that works on both iPads and iPhones?