I didn’t find a good answer online when I ran into this issue, so hoped I can be the answer for people who have this same issue in the future.
We recently got Chromebooks for our kids to support their remote school for the rest of the school year and I wanted to set them up with monitoring – Google has a tool to do that called “Family Link“. We set up accounts for our kids, but unfortunately, we received an error when we tried to log into the Chromebook:
There weren’t any details (and my parent account could log in just fine) – searching online came up with a bunch of frustrated posts that were almost a year old and talking about the change from supervised accounts and how Family Link didn’t work on Chromebooks. I received that error when trying to add a new user or log in – I couldn’t complete either process.
Looks like your google account can't go here
The secret ended up being that the ChromeOS on my Chromebook was CRAZY out of date – even though it was ordered brand new from Amazon, it was running ChromeOS 56 when the CURRENT VERSION (as of March 2020) IS 80! All of the documentation I saw on Family Link said it that required at least ChromeOS 71 and this obviously wasn’t cutting it. I would have expected a brand new Chromebook to be updated to something near current, but obviously not – according to https://www.chromium.org/developers/calendar, version 56 was released in November 2016 and is over 3 years old at this point
It doesn’t prompt you to automatically update to a newer version of ChromeOS – you have to do it manually. To do that, go to the system info in the lower-right corner and click on the gear to open settings, then click “About Chrome OS” at the top, then “Check for updates” and apply anything it shows. In our case, it updated to 72, rebooted, and the applied a few more security updates and a few more reboots before it finally landed on 80. Once it did, I could log in with the family link child account, approve my child’s sign on, and we were on the way with no more problems.