I just got a brand new Netgear Orbi router with extender (called a satellite) this weekend. When navigating to the firmware upgrade page, the UI indicated that I had an upgrade available for the base station, but the satellite unit was stuck in "please wait" mode. So, I decided to try upgrading the firmware manually. I read online that you should always upgrade the satellite first, so I downloaded the firmware for both, logged into my router, and attempted to upgrade. I was then presented with the following error message when attempting to load the firmware for the RBS50 (the satellite):
After a little poking around, I realized that my satellite appears in the list of "attached devices" and when I connect directly to the satellite, there is a different interface for upgrading the firmware of that device. So, I used that interface to upgrade just the satellite (the RBS50). Once finished, I could upgrade the firmware of the Orbi router using the automatic upgrade feature.