If you receive the following error on signing in, it is likely that your Role/Role Document doesn't contain the Read User permission, no cloud accounts are setup across the available clouds, and the Role/Role Document doesn't give access to setup cloud accounts across any of the available clouds.
Please have your platform Administrator validate that your Role/Role Document currently contains the following permission - Setup -> Users -> Read User, as this permission is required at a minimum for the platform to operate correctly.
Once enabled you will find the next time you login that you are redirected to Setup -> Admin -> Users rather than being placed into the above redirect loop.