If you sign up through the Apple App Store and not fotoShare.co, make sure that the device you are using is logged in to the App Store using the same Apple account you used to purchase the subscription.
For instance, if you purchased your subscription with an Apple ID, ensure that the same Apple ID is logged in on the device to avoid recognition issues.
To restore your subscription on the same device after a reinstall or on a different device, go to Settings, Account, and Restore Subscription.
Restart your device to refresh system settings, then reopen the app and sign in using the correct account details.