How to reset or recover password on allied telesis x900-24xt

What exactly is the problem? Does it post? Does it get stuck when the OS is being installed? If it posts, you may have a bad hard drive, corrupt OS, bad memory, bad peripheral,

If no post you may have a corrupt cmos and be in deep doo doo because you cannot repair or re install an OS.

Go here:
Allied Telesis AT WL2400 802 11b Wireless Access Point

The default password is the only one available

At the login prompt, enter the login name and password as follows:

Login: manager
Password: friend

Forgot or lost the password
Contact Allied Telesis Technical Support for assistance.

Did you make a configuration backup record?

All I can give you is the Google search links to the reference guides.

Here is a link to a PDF for a guide for the x600

follow this step

KIMIA# delete
startup-config Delete startup configuration (Reboot from defaults)
flash:// Delete a file from the flash (flash://filename)
WORD Specify name of file
KIMIA# delete startup-config
<cr>

KIMIA# delete startup-config
Delete startup-config [y/n]? y
Startup file was deleted
KIMIA#

User Name:manager
Password:friend

console#
console#

Here is a link to user manual for Centrecom models :
- You may need to directly contact at Allied Telesis to find replacement parts

https://www.alliedtelesis.com/sites/default/files/at-6870_at-6875.pdf

Contact information is at the end of this manual

The Allied Telesis website says this:
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How do I recover a lost user's password on Layer 3 Switch or Router? ...

If a user forgets their password, the password can be reset from an account with MANAGER privilege, using the command:
SET USER=login-name PASSWORD=password

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Another website has this to say:
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device has a reset button.. you can push that via pen, check the devices handbook you will see that mini button..

push that button for a ten second... and release.. your settings will reset.. default username : manager password: friend

try
usename: manager
password: manager

also try
usename: manager
password: friend