I have a C8 which should be about the same.

Remember - If you have used any network in the past with the same SSID and password, your computer/tablet/phone will connect without asking for the password.
Also make sure your device is connected to the new guest network and not some other network.

Assuming that is not the case, when you set up the guest network

Turn off any Access and Bandwidth control
Use a unique name for the guest network (never use any default name, do not use something common like Guest, nor any other SSID used in the area)
Be sure you have the "wireless Security" set to WPA/WPA2.
Set Version and Encryption to Automatic
Set up a secure password
Hide SSID does not matter as it does not really hide it.
I would leave Access time off and set it later if needed after it works like you expect.

If you set up multiple networks, use different network names and passwords.

Hope this helps.

Hi
Thanks for responding
Your advice helped me set up properly.
I had not done it correctly to start with.

Thanks again