This is from Apple support. Is it like what you get?
If iOS detects an issue with your Wi-Fi connection, you might see a Wi-Fi recommendation under the name of the Wi-Fi network that you're connected to. For example, you might see the alert "No Internet Connection". To get more information, tap the Wi-Fi network.
Also check that the Apple device still has an ip address.
Do the Apple devices get good signal strength?
Check the system log on the wifi router.