If you purchased a refurbished product by Netatmo, it has been refurbished in a reconditioning workshop where it was validated by tests that meet the same functional requirements as for a new product. All data possibly present before the refurbishing has therefore been permanently erased.
If you purchased a second-hand product (not reconditioned by Netatmo) from an individual or from a distributor, the product may not have been reset. In this case, it will be automatically reset during its installation via the Netatmo application in order to erase any possible trace of a previous configuration.
Updated