The previous configured password is typically what you are behind.
Keep in mind as a part of the continued security updates, the ProSAFE Plus Configuration Utility is obsolete, recently updated switches don't accept any configuration or password changes (unless this was explicitly allowed, permitting the old NSDP protocol access. Strictly focus on the Web UI available on all newer recent models for admin purposes as documented https://www.netgear.com/support/product/gs105ev2.aspx#docs (except of the obsolete ProSAFE Plus Configuration Utility).
