Error "Login to(Catalog) Unknown error occurred while login" appears when logging into CA Service Management Mobile application using Unified Self-Service (USS) URL.
The authentication type set in Catalog is set to "Artifact Based Single Sign On" but no SSO is being used.
1) Log into Service Catalog as an Administrator > Administration > Configuration > Single Sign-on Authentication
2) Set "Single Sign on Type" to disabled > Save
3) Log into Mobile app using USS URL