iWeb no longer opening projects?

I am trying to open and work on half a dozen websites done over the last five years. I can't.

The last time I double clicked open a Domain.sites file it would open in iWeb and I could make and save and upload changes. Now those same Domain.sites files open into a blank iWeb project ... If I 'Show Package Contents' all my original pages and graphics etc. are still there in the project file. But it will not open in the iWeb app.

Is there some way I can open these projects?

I know iWeb is no longer a viable app with Apple. I'm trying to rescue these projects and move them to EverWeb. But if I can't open them in iWeb, this will be a nightmare amount of work. Help!

All ears,

Ben