Home Wifi issues with new iPhone 16

I'm presuming that the Wi-Fi signal strength shown on your iPhone is good and remains so as you try to use it. If so, you can try forgetting the network and reconnecting. If that doesn't help, try resetting your Network Settings in the iPhone:

Settings > General > Transfer or Reset [Device] > Reset > Reset Network Settings

If that still doesn't help, try Wi-Fi at another location or two. If it works properly there, then I would have to suspect an issue with your router or your Internet service, though one final thought: if you have any sort of VPN on your iPhone, disable or remove it and see if matters improve.

Regards.

Have you tried restarting your Wi-Fi router?