Symptoms
After renaming k2 sites from k2.denallix.com to other.denallix.com and then running the K2 blackpearl Setup Manager so that K2 can pick up the changes. After configuration completed, he saw a "No permissions to consent" error.
Diagnoses
The SmartForms setup manager was not re-run to update the SmartForms related settings. This meant that the following web.configs still had the old k2 site URL in the realm value.
"C:Program Files (x86)K2 blackpearlK2 smartforms RuntimeWeb.config"
"C:Program Files (x86)K2 blackpearlK2 smartforms DesignerWeb.config"
Resolution
After manually updating the web.config files to use the https://other.denallix.com host header, everything was working as expected.