This has been driving me crazy every couple of weeks for months now...
I have two primary google accounts. One is my private account, the other is the corporate administered account. We'll call the first A and the second B.
I am (usually) able to work comfortably with both accounts open in Chrome, e.g. one tab for gmail A, one for gmail B. So far so good. Chrome is synced to A
Then, I'll open a tab for Google Maps. I am not signed in to the app at this point. I click sign in, and am presented with the login screen for B. I click sign in as a different user, and get a very incorrect (from my perspective) response, telling me that "You are trying to access Google Admin of {B}.com but you do not have a valid logged in account for it."
(Sorry for the bookmark tooltip...)
So, without logging out of account B, I don't seem able to log into Maps with account A.
This experience is a lot like biting into a pebble in a bowl of pasta.