That message is typically displayed if there is significant radio interference around your home. This interference causes your WiFi signal to become weaker than normal resulting in slower speeds, intermittent service drop outs or messages saying the "connection is not secure". You said that your connection over Ethernet never encountered this issue. Is this for the same computer connected to WiFi vs Ethernet? Would you be able to provide more detail on what you're experiencing overall? Does this happen on multiple devices/computers or just the one main one? We'd love to help.