Hi there
Is there an exclamation mark next to the WiFi icon? If yes, it means you have no connection from your router...
If no, please put Airplane Mode on and leave it for about 20 seconds, then turn Airplane off and see if that fixes your connection.
Is your phone WiFi connected to your home WiFi or has it picked up a neighbour or BT WiFi public? If so, force forget that connection then manually select your home WiFi.
I'm presuming you having m haven't changed your WiFi passwords and your phone has the correct one?
Hope this helps.