Cannot access RBK50 Router from either wireless or ethernet after shifting to access point mode

I read a similar article with those options listed.  So I tried the third: access point mode. After shifting to Access Point and having trouble reaccessing the RBR50 (orbilogin.net or any of the IP addresses) is why I started my question in this forum.

The problem was that I could not get the modem/router (C2000T) to ever recognize or provide an IP address: the modem shows under "Ethernet Status" that some unknown device with a MAC address is connected to the ethernet port (does not provide an IP address in the table), but in the "Device Table" listing devices and IP addresses, it does not show any active (or inactive) device with that MAC address).  

With the RBR50 either connected to the modem or not connected to the modem (I tried it both ways), I have been able to log-in to the RBR 50 both wirelessly and by ethernet cable from my laptop (while simultaneously logging into my modem from my desktop).  But once I shift the modem to Access Point, my laptop can still "see" the RBR50 through the ethernet cable ("Unidentified Network, No Internet) and can log-in to the SSID (No Internet, Secured).  However, I cannot log into the RBR50 (orbilogin.net or any other IP address) itself.  The only IP addresses for the network setting (Windows 10) are the IPv4 addresses for each of the RBR50 channels (169.254.xxx.xxx/16).   I tried using those (with and without the "/16") in two different browsers but to no avail.