New-to-me Orbi Router--Firmware Update Fail

First:  If you haven't performed a factory reset of each device, it is recommended that you do so.  With each unit, allow it to completely boot up (2-3 minutes), then press and hold the reset button for 7-8 seconds until power LED begins to flash orange/red and release immediately.  It should go dark for several seconds, then reboot itself. 

Second:  I would try Internet Explorer as the browser for this project since the others don't seem to work.  In Windows 10 it can be found under All Programs -> Windows Accessories.  

Third:  Wouldn't hurt to connect your PC to a LAN port on the RBR50 via wired ethernet if at all possible..  

Fourth:  I have seen more than one of these devices be very particular in stepping through the manual upgrade process.  You might even consider "downgrading" to a 1.8.0.6 version of firmware, then working your way back up.  I experienced one brand new router which started at 1.8.0.6, had no problem manually updating to 1.12.0.18 and would only jump into the 2.X firmwares by starting with 2.0.0.74. 

Lastly: Make sure satellites are upgraded to the same FW version as the router before syncing for the first time.  For manual updating, a factory default satellite will have an IP address of 192.168.1.250.  A factory default router will have an IP address of 192.168.1.250.  For either, Username=admin, Password=password.