More information to feedback from my troubleshooting. I had found that 2 of my 3 Nest Protects were reporting NULL for smoke and CO (although battery was being reported). I find I can reliably fix this by going into the NST Manager on the Smartthings app on my phone and simulating a smoke/carbon/low battery event. This shows up in the Smartthings log, the Openhab log and triggers Openhab to report real data.
