@aufdenkampe, in my spot checking on the staging portal, I haven't been able to get any WDC service other than NWISUV & NWISDV to successfully generate plots in the detailed view. Even NWISGW. I've tried CocoRaHs, GHCN and NWISGW.
The NLDAS gridded service also fails to grab and plot data, but the failure manifests itself differently on the portal (not with the red warning icon next to the variable).
This makes me suspect that the problem is in the portal, not the GHCN service as Terrance thought today.
I'll try to do more digging today or tomorrow.