Airport Express failing to extend network

Hi,

I've been using Time Capsule, 2 Airport Expresses and and an Airport Extreme for a few years without a problem. A few weeks ago, I noticed that on of the devices which I hadn't looked at in months was flashing amber with a WDS error. It took me a few hours, to resolve, but I reconfigured every device and got everything working again. Yesterday, everything except for the Extreme was flashing amber with the "Extended Network" error. I've turned everything off except for the Extreme. Forgot all of the others. Turned on a single Express, but can't resolve this issue.... I've included a screen-shot of the current error. It suggests to confirm the password, which I have.... The "other WiFi Device" indicated at the top of the screen shot, is the "Family Room" shown in the image.

Currently,

Can anyone help?

Thank you...