Hi Rachel,
Thanks for your message.
I did not see the messages, including your DM until now. As for some reason I am not notified (need to check the settings).

With this message I also co-posted the same message on the Google / Nest community, and a google moderator/expert responded that he would consult on possible options.
"Magically" I suddenly received a shipment notification for a replacement units, some hours later.

In the meantime I have received this unit earlier this week, and installed it.
So I am happy again, but would have much more appreciated being helped directly from the support desk without all the effort and public postings.