Viewsonic Panel not "freezing"

[Smee]

We have several new viewsonic panels but the freeze function on the remote doesn't do as expected. All we get is a black screen with a lock icon. I've been in touch with the boards support but they don't seem to be having any joy. The computers are connected via VGA, computers too old for HDMI. They did work for a couple of days when first installed and as far as I can see nothing has been changed. Hopefully I'm missing something obvious. Any suggestions please?

[ViewSonicService]

Dear Customer

We apologise for the issues that you are having. May we kindly confirm where you are based? You can contact the ViewSonic service team by logging a ticket at https://www.viewsonic.com/eu/contact/ for our direct and prompt support if you are in the European region, or https://www.viewsonic.com/us/customer-service-form if you are in the US.