Wifi Extender Ex2700

Hi i recently purchased a wifi extender to extend my wifi network. I have an apple airport express that i am trying to extend its signal. Now ive gone through the setup multiple times, entered a username, password and then succesfully connected it to the airport express network. Now when i go to my wifi selctions at the top of the desktop screen( i am running Catalina on mac mini) i see the airport express wifi network and i see the airport express network ext. ( which i assume is the new network i setup) Although it says the new network has full signal but when i click on it to use it i cant use the internet. Am i missing something, do i need to actually click the airport express network ext. on the wifi selction to use it or does it mean by extending the network i only need to select the original network.

    if anybody has any solutions i would be glad to hear it thanks