The most common reason for a device to connect to Wi-Fi but not have Internet access is due to issues with DHCP. This could be because the device did not obtain an IP address correctly, or the DHCP server is not functioning properly. Checking the DHCP settings and ensuring the device is properly receiving an IP address is a critical step in diagnosing connectivity issues. SSID mismatch refers to the device trying to connect to the wrong network, which would prevent connection entirely. If the subnet mask is incorrect, the device might still get access to the local network but have issues reaching other networks, though it's a less likely scenario. Incorrect WPA2 key would prevent the device from connecting to the Wi-Fi network in the first place, not from accessing the Internet after connecting to the Wi-Fi.