Creating a task from a Guided VTB (Visual Task board) on the task table does not work for non-admin users.
Out of Box the task table does not contain the default security rules (Read, Write, Create), only admin have access to it.
Create default security rules (Read, Write, Create) on the task table. Add the role the needs access to that task table on the ACls.
Note: It is not best practice to create tasks directly on the task table. Instead, tasks are created on task child tables.