Orbi RBR50 can't login online and cannot detect router using app on phone

Please help.  Our Orbi router is not connecting to the App.  This router was installed in Dec 2018 and things had been working fine until recently.  We were trying to troubleshoot a problem with our Hue lights (which had also been fine until about two weeks ago), when we discovered that we could not access our router using the app. We get an error on the Orbi app "Issues connectig with " wifi name. We have verified that the phones are on the same wifi network, but we continue to get the same error. We have tried to restore the device to factory defaults and use that wifi name and password. That did not solve the problem.  When we try to use a computer to access Orbi using orbilogin.com or orbilogin.net, we get a message "internal server error 500."  We even get this error when we have an ethernet cable directly connecting the Orbi router and the computer.  Interestingly, we have wifi access as I am logged into my Orbi Wifi network now as I type this message. The other thing that we noticed is that when we reset the router to the default network credentials (what's on the label at the bottom of the router) the wifi credentials we had been using did not disappear.  We are unable to get to the admin page for the device because we do not have access to orbilogin.com or the orbi router using the app.