Sometimes you need to connect the device running the photo booth app to a Wi-Fi connection that might not have access to the Internet (for example, when connecting wirelessly to a GoPro, or a wireless print server).
If your device has cellular capabilities and a SIM or eSIM with an active data plan, you can still provide access to the Internet by using mobile data. In most cases, your iOS device should automatically detect that the Wi-Fi connection has no Internet access, and any network request will be sent over the cellular network instead of Wi-Fi.
Troubleshooting Cellular Internet Issues when Connected to Wi-Fi
If the Internet requests in the app fail after connecting to a Wi-Fi network that does not have Internet access, there are a few things you can try:
Temporarily disconnect from all Wi-Fi networks, and check if the Internet is working over cellular (either in the app, or by trying to load a website in a browser). If the Internet is not working at this point, make sure your data plan is active, it has available data, and that your device has cellular service. Once your mobile data is working, reconnect to the Wi-Fi network, and then try the next troubleshooting step if the device still can't access the Internet.
Make sure that cellular services are enabled for the app. You can check for this in the Settings app > Mobile Data.
If the app still can't access the Internet, you may need to force iOS to recognize that the Wi-Fi connection doesn't have access to the Internet. Follow these steps to do this:
Go to the Settings app > Wi-Fi.
Click the info icon (β) next to your current Wi-Fi network.
Make a note of your IP Address and Subnet Mask.
Change Configure IP from Automatic to Manual, and enter the IP Address and Subnet Mask you took note of before. Do not configure the Router field. This should be left blank/empty, and this is what forces the device to use the cellular network instead of Wi-Fi for Internet access.
Save your changes. The device should say "No Internet Connection" next to the chosen Wi-Fi network.