Satellite asks for user name and password - won't accept the correct one

[AndrzejBania]

MANY, MANY people have posted a version of this question here - going back to 2016 - but I cannot see a DEFINITIVE answer from Netgear.
I want to update the firmware on my router and satellite.
I log in and do a manual update on the router - very simple.
I then tick the box to do the satellite and I get a pop-up asking for the user name and password.
It won't accept them. 

I tried several times - no luck.
I go to the main router and change the password...   Successfully.
I log out.

I log back in.
Try to update the satellite firmware...   It asks for a username and password.
Nothing works.
MANY, MANY people have asked a version of this question.
I see no definitive answer.
Help!

[AndrzejBania]

With the satellite on, pin into the RESET hole until it flashes ORANGE.
Press RESYNC on the main router, then resync on the SATELLITE.

It will flash blue for a while - but will now accept the correct username and password.

[FURRYe38]

Did you factory reset both router and Satellite. Set up router first with PW. Don't change the ADMIN user name.

After the router is setup, setup the Satellite, when it's sync'd, the Satellite should get the same ADMIN and password thats set on the router.

Have you upgrade FW? You should try the new Beta. Factory reset after installing and set up from scratch.

[st_shaw]

Always update the satellite first.