This error usually occurs when you share workbooks with coworkers, or after a computer move or rebuild. Analytics Edge stores a reference to the account in the workbook, but the actual security tokens are stored on your computer.
To fix this problem, simply add the missing account to your computer. Note that you should use the exact same reference name so your existing queries will run. The missing reference name is usually in the error message itself.
Newer versions of the connectors may automatically pop open a login dialog for missing accounts.