firmware updates were completed over the weekend to 28.6.1. with no resolution in the senor issue. The three sensors that I have appear to come up for a while and then no longer report to the dashboard. I have also pulled the batteries, factory reset them, and removed and added them back to the network. Same issue. Still working on it and I have opened a case. Meraki is slow to work on this through the case so I will probably have to call them.