I contacted Nuki support to explain the issue I described in this post:
It has been weeks (or even months) that we’ve been communicating via email, and we’ve tried all the suggested solutions. They even sent me a battery compartment to test with alkaline batteries to rule out any issues with the Nuki Power Pack.
After all these tests, along with photos and videos sent, they told me they unfortunately cannot proceed with replacing the Smart Lock because I am unable to provide them with an invoice.
As far as I know, the warranty from the manufacturer is still two years. Additionally, when I bought the Smart Lock, it arrived sealed.
Could anyone clarify this for me? Thank you.