Hi there! I understand your CUSTOM CAST app keeps telling you to check your WiFi connection. Just to get us started, can you tell me if other apps or devices on your Android 10 WebKit device can connect to the internet without any problem? Also, does this issue happen only when using CUSTOM CAST, or do you see this message frequently even with stable WiFi?

Once I know a bit more, I can guide you through some steps to fix or narrow down the issue. Meanwhile, a few initial things to check:

1. Ensure your Android device is connected to the correct WiFi network and the connection is stable. You can toggle WiFi off and on to refresh it.
2. Restart your Android device to clear any temporary glitches.
3. Sometimes, routers block certain devices. Make sure your device is allowed on your WiFi through your router’s settings if possible.
4. Verify that your CUSTOM CAST app is updated to the latest version available on your app store.

If these basics don’t help, we can dig into more advanced settings like checking WiFi frequency bands (2.4GHz vs 5GHz), resetting network settings, or looking for conflicts with other apps.

Could you try those steps and let me know how it goes? Also, if you get any specific error messages or behavior, that would help me assist you better!