We are tryng to clear a 911 notification from the display. We do not have a 911 display clear key so need a key sequence if there is one.

I don't believe there is a key sequence. I am pretty sure a 911 Clear key has to be programmed.

Unplug the phone for a few minutes and then plug it back in. See if that helps, if not it might require a reset or a 911 clear key.