Connecting my various devices to Wi-Fi

I have about 10 devices (apple and non-apple) in my household. All, along with anyone else that visited, were able to connect to wi-fi previously with no issues. I changed out my old cable box today and after that I had to reset my modem and my Airport Express router (both over 5 years old). After doing so, only some of my devices could still connect to wi-fi. I reset them again, and lost wi-fi on the previously connected devices but gained it on a couple others. Any idea how to get it back for all of my devices?