ReadyNAS DUO RND2120 Password reset

I have an old ReadyNAS DUO that has been out of service for a while.

The admin password is no longer known, nor is the password recovery answer.

My understanding is that the default credentials ought to be

admin password ( all lower case, no punctionation, no numbers)

When I got the NAS it was configured with a hostname, static Ip address and had a password recovery page option.

So far I have:

performed a password reset via reset button

    hold reset in for 5 seconds, wait for boot to finish

made absolutely no difference ( I understand this option has to have been enabled first, before it will work)

Then performed an o/s reload

   hold reset button in for about thirty seconds until disk leds have flashed twice.

   left unit on overnight

unit has now defaulted to be a dhcp client, with host name of NAS-77-B7-C5

RAIDar shows it as ReadyNAS DUO, Healthy, firmware version 4.1.8

Attempts to reach http://{ipaddres}/password recovery now give a 404 error

logging in to http://{ipaddress}/admin does NOT allow me in with admin / password

Tried using Edge on Windows 10, Chrome, Firefox and IE11

One:  does the change of hostname and IP address mean the O/S has been sucessfully reloaded ?

Two: should the default admin login now be admin / password ?

Three: Is there any limitations as to which browser I need to use or special settings. ( I have already told all my browsers to ignore certificate errors)

My final option is to do a firmware re-load. However, I am not sure;

a) where to get the firmware source (i.e. what version do I need ? )

b) how to perform a local install. Is this by using one of the two options TFTP Boot or USB Boot ? If so, how do I configure the source ?