When you enter Google Play or App Store link in "Application URL" field while setup campaign then the platform will automatically validate the app and shows it's details but in case it does NOT happen then you can hit "Validate" button to force the validation process.
Note: Our system validates app in US market so, if your app is NOT available in US then you may get validation error or could not resolve error.
Still Getting Validation Error?
Note: Use "Skip Validation" button only if you believe that your app is live in the Play Store (or App Store)
Advanced Solution for some Rare Cases: