If you need to facotry reset an Ava Server that you have no access to, e.g. an on-prem Appliance where the password has been lost and there is no means of recovery, then the server can be factory reset as long as you have physical access.
To do this, connect a keyboard and mouse to the server and power it on. At the first Ava boot screen, choose to boot from the Primay partition and press enter. At the next screen, choose "Factory Reset". The server will then boot up the OS, then ask you to confirm that you wish to factory reset. Type "Yes" and press enter. The server will then restart and boot up in a factory reset state.
Caution: This process is not reversible, and all config and video data will be lost unless you have a config backup for the server.
See also this video which shows what to expect to see from a connected monitor when the server boots up;