I initially had problems with the website/app on Iona in August. When switching to 4G from the onboard wifi it nearly always had an issue reconnecting to the wifi/app when switching back. To start with I found a reboot of my phone sorted things. I then found switching off private wifi address and limit ip tracking meant I could switch between 4G roaming and the App at will. This might be specific to iPhones and if you have an iCloud subscription