Why does Airport Utility say Device Not Found?

[prefersmac]

I have macOS Mojave v.10.14.6. My Airport Time Capsule was purchased in 2013. It is 5th generation and the firmware is v.7.9.1. I use it as the Access Point for my wireless network. It is in Bridge Mode. It is plugged into a network that already has a router. The Airport Utility says "Device Not Found...[Forget]"? What should I do? Thank you.

 

[prefersmac]

Since I do not see this issue on my iPad (iPadOS 13.2.3) nor my MacBook Pro 2019 (OS 10.15.1) I assume it is related to OS Mojave and I will ignore it. If I need to access the Airport Time Capsule settings in Mojave I can switch my 5Ghz connection to 2Ghz which normally clears the "!ATC Device Not Found...[Forget]" message.