Try Internet Explorer (yea we know but it is still available and it what most of these systems were written around).
Which device - camera or NVR? These devices are connection and bandwidth limited and if too many devices are trying it can stall out.
What are the specs of the two computers? One that isn't up to the task can stall on live view.
The "opening live view failed" is usually a network bandwidth issue, but a slow computer or too many connections to the device can cause that as well.