I did get ahold of google support and a replacement was sent to me.
There is a select few nests that they know of with the software issue.
They even offered to pay for a inexpensive one until the replacement
nest arrived.
Exact same thing is happening to me - not able to connect to wi-fi 2
errors m5 and something else - won’t hold a charge, won’t connect to
wi-fi and stopped working, trouble shooter through each error message…No
luck. Not going to buy A new one. Hope ...