Symptoms
View Flow Permissions
Diagnoses
For some users the viewflow loads, while other folks gets prompted and seem to get stuck on some redirect that goes through:
http://dlx:81/identity/sts.windows/wsfed?blablabla
Resolution
Issue was resolved by re-ordering the Providers (setting 'NTLM' to be first) for the K2 web application > Identity > Sts > Windows > Windows Authentication > Providers.