Multiple Website for Different Clients

Hello,

I downloaded WordPress and am trying to create websites for multiple clients. The first site worked fine, but the other sites I created will not let me use the Customizer and will not update when I install new themes and plug-ins.

I didn’t create the sites myself, but had someone else lay the foundation on the webhost then give me the log in info so I could design the sites. Where did we go wrong?

Thank you!