devices not seeing one of networks, ac1900 wifi range extender model EX7000

I installed the nighthawk ac1900 wifi extender, model EX7000 a few days ago. Everything was working great, my devices could see both networks and i could connect to them. I downloaded the latest firmware. The past few days, my devices can not view one of the networks, either the 2G or 5G. It depends, usually I restart everything and they both show back up for awhile, then one disappears. The extender itself says that everthing is running fine, both networks are green and ready to go. Miwifiext.net also shows that both the 2G and 5G are running at full power. But my devices: iphone 6s, macbook pro, xbox one, vizio 4k TV only can see one network. A representative had me reset the extender and install again last night. Again, both networks were visible to devices and everything was fine. But this morning, the 2G disappeared again to all devices. This is driving me crazy. Any ideas? Thanks for any help.