It's pretty normal for most perennials to have flowers for a week or two tops out of the season. I haven't grown this particular coreopsis, but most of the ones I've grown have been basically like this. However, most coreopsis will rebloom a little bit if deadheaded, unlike say a peony where that's it for the year.

And yes, you can definitely use scissors to cut it back -- I'd say you can cut as much as about half of it off, water and maybe give it a shot of miracle grow or similar, and it should bloom again in a few weeks, but not as heavily as the first time.

Maybe someone who has grown this particular one will chime in with a better answer, but I think I'm at least in the ballpark.

CB blooms for a very long time, I suspect it lost blooms due to transplant shock and/or it started blooming a long time ago in the greenhouse.

It has never returned for me after the first winter.Nobody is selling it here in Denmark anymore.