This is because you have to download the gradle files first before running it. Follow the steps and it will definitely run.
* Step 1: Clone the project from github repo.
* Step 2: Open it in any code editor (I prefer VS code).
* Step 3: Install node_modules by running npm install command in terminal.
* Step 4: Open android studio and open the react-native-app/android folder inside it.
Note: Android Studio will automatically start downloading the gradle and build it, which you can see in bottom part of android studio.
* Step 5: After gradle files are downloaded and build successfully, go back to the code editor and try to run your app again using
npx react-native run-android