Hmm... Could be a number of things. Without the phone make and model it may be hard to get the correct solution but here goes. Firstly is your mobile set to "Encrypt" Phone Password. If so it will probably require a factory reset. Leave that option for now as you will lose all data if you have not backed it up.
So Firstly, try a reset of the Wifi Hub. You will need a pin or needle and you need to press for about 20 seconds the little recessed button that says "Reset" on the back of the hub. Before you press that switch off mobile phone Wifi. When the hub has reset start up the phone Wifi Scanner and try again.
If that fails. Try this. On your phone , Go to Settings ...Wifi and click on your network. Click to forget it. Rescan and click on your network. Enter your information as you normally would, but click advanced before confirming and go down to IP Address. Change from DHCP to Static. Go to IP Address and change it to something like 192.168.1.77 for example. Just confirm and hopefully its rectified.
When you get chance Tills try those two things. Good Luck.