We are able to register new users and these create user tasks submit successfully.
But in View My Worklist they do not appear.
From the approver group, one of the managers removed all User ids except one id.
Make sure your workflow configuration specifies all the users who need to be approvers.
For example for a Create User Task, in Roles and Tasks --> Modify Admin Task --> Create User
On the Profile page, click Workflow Process, select your workflow and configure users that should be approvers.