Unable to access my new printer HP Envy 6455e, have MacOs Sierra version 10.12.6?

A new HP printer will not have HP drivers available for an 8-year-old operating system. Although Apple's built-in AirPrint supports this HP device when networked with current releases of macOS, I question whether AirPrint on macOS Sierra knows about this device unless Apple resolves it from an AirPrint server. You can try it and if it doesn't work, then you will need a much newer Mac capable of running a current macOS.

Ensure that your HP 6455e is powered on, and uses either wired or wireless networking. Visit System Preferences > Printers & Scanners panel and click the + symbol below the Printers panel to add a new printer. If your 6455e is detected on the local network segment it will appear in the Add dialog that is now present. You select the device line and that should automatically apply the AirPrint configuration; Provide you with an AirPrint selection option, or Choose a Driver. The latter would indicate that AirPrint doesn't know about your device. Otherwise, click Add. Your scanner support would then be from Apple's Image Capture, or if you choose, the optional, paid VueScan Professional that supports this scanner component without any HP drivers.

The add printer should work as it does for my pre-2014 Samsung ML2955ND laser printer: