I'm using Macbook Pro with 10.11.6 Until a week or so, I used Airport Express, and older model, as WIFI base station. It has worked well for years, but I began to have problems with interruptions on certain web pages, problems that went away when I went to other locations using other wifi. So I thought interference and weak wifi might be the issue, neighbor's wifi, etc. So I upgraded to Airport Extreme. New wifi seemed to work better but I realized i had lost Airplay, which I use a lot. So i have been tying to add the Express to the network, only to get the message "This version of Airport Utility doesn't support this base station" regarding Express. Which is odd, since until I changed to Extreme, the Express was working just fine. I suspect something else is going on, but don't know how to diagnose/fix. Any help appreciated. Thanks!