Wifi range extender password issue

Thanks for the suggesting the most obvious, trust me I have tried this at least 50 times over and over again. I am not using the factory password and rounter name my router came with - I have both customised to names/words that I have chosen. It picks up the customised router name for the ext which is the custom name of my chosen router name + ext but when it comes to my chosen password it does not accept it. I somehow have now managed to go into the router settings by going in via http://192.168.1.250 but when I look into the back end it says the ext has the same password as my router which clearly is not the case so I'm still stuck with the same issue which is getting rather irritating :(