This issue is resolved. Please report any additional problems to CCR Help
We are aware of a problem for users that have two-factor authentication enabled that are trying to connect to cluster front-end nodes via SSH. As a work around while we troubleshoot, please use the OnDemand web portal and the cluster app to access the shell.
OnDemand documentation - https://ubccr.freshdesk.com/support/solutions/folders/13000014606