I am trying to set up a Google Apps account on Yosemite. I can log into the account, up until where I select which services to active. It will only activate Contacts and Messages. Mail, Calendar, and Notes will not activate with a very generic error message:
An unknown error occurred.
As part of a migration, I first tried adding the account next to the 'old' account, which gave all kind of errors pertaining to Yosemite not liking it that I wanted two accounts for the same email address. Maybe there still are some remnants of that, that I should clean out, but I don't know how.