Check connection prompts on both phones and confirm that neither has switched to a different network. If the app still cannot connect, try again on a trusted Wi-Fi network that allows device-to-device traffic. The exact ports needed depend on the app implementation; this website does not specify port numbers that have not been verified.
Keep both devices awake and close enough for a stable wireless connection. Check available storage on the receiving phone. If a large batch fails, try a smaller selection and check which files were already copied before restarting. Transfer speed is not guaranteed and depends on the devices and connection.
Check the Download folder on the receiving Android device, then check the destination folder selected in the app's settings. Confirm in the app that the transfer finished, and open one of the received files before removing the original.
Internet access is not required for local file copying. A shared Wi-Fi network is required for this app, even though it then uses Wi-Fi P2P for transfer. A phone-created hotspot has not yet been verified as a supported setup.
The described workflow requires the app on both Android devices and uses Wi-Fi, not Bluetooth. This guide does not claim compatibility with iPhone or PC.