Symptoms

When trying to access K2 Management the following screen was had:

Access Denied

The K2 Management site is used to configure and administer K2 server, workflow and SmartObject settings. You must have Admin privileges to access this site.
Contact your K2 server administrator if you need rights to administer K2.
 

Diagnoses

Two accounts

One with proper K2 server rights and one without. The account oAccount]@domain.com was logged in to O365 but did not have K2 server rights. Where as the account oAccount]@differentdomain.com did. The cookie storage for the browser session had already been filled with the former account information.
 

Resolution

By starting an incognito browser session we get a separate cookie session and then leverage that to log in as the differentdomain.com account which has K2 server rights. From there:

1) Go to K2 Management

2) Drill down into Workflow Server>>>Server Rights

3) Add the other account to the Server Rights list and give it Admin, Export and Impersonate rights.