RBS850 - Updating to Firmware 7.2.6.21 - now remaining satellites won't accept admin/password login

No it does not.

Each satellite typically has one dedicated network cable leading back to my central switch so all are on hard line connections to the RBR850 Router.

Each also has several local devices that are also plugged directly into the other there ports on the Satellite.

For this exercise, per your suggestions, I unplugged everything and then connected a network cable from my USB C adapter plugged into my MacBook Pro into the first port on the back of the Satellite.   

This adapter is the same one I use at my desk for a direct cable connection into the house network so no question that it works.

When the Satellite comes up, at first there is no network connection at all - then it becomes a self assigned network address, and then if I let it sit long enough, the satellite will connect via the WIFI backhaul to the Router - receive its dedicated IP and then hand my MacBook Pro an IP address from within my normal network block.

When this happened with the first satellite, I then tried its IP address, got the login screen - typed in admin/password and was able to do the update.

After the update I could log into the satellite directly.

I then went up stairs to where the second satellite lives and tried the process there - only this time no matter how I reset or power cycle after or before a reset, the direct connected network cable only gives me a self assigned value and then eventually my expected house network value.

I have tried setting the laptop itself to 192.168.1.10 and then when the Satellite starts to pulse white, entering the IP address of 192.168.1.250 into the browser - but it fails to connect to anything.

The Satellite that I did update - now again I can't connect to it via its portal - the admin/password just cycles back to the same screen and then a forbidden notice.