Home WiFi Issues w/ AirPort Time Capsule + AirPort Extreme

Comcast is our internet provider and I've owned a single AirPort Time Capsule for some time. It's worked as our home Wi-Fi up to this point (as well as backing up main computer). Wanted to extend our home network coverage. Recently purchased a AirPort Time Capsule and placed it downstairs (simply plugged in to power). Since that time we get "No Wi-Fi Connection" messages at times on our iPhone's, iPad's, etc. This never happened before. Kids Xbox One chat functions don't work since this Time Capsule addition as well (also never had issues before). Hoping someone smarter than me can shed some light on this with some tips or tricks 🙂 Thank you!