I recently installed an Archer a10 in my home, along with 3 powerline extensions. One of these is mesh enabled, two are too old for that but work nonetheless.

I set all devices with the same admin password and confirmed all were working. Today, a few weeks later, I try to log in to the admin page of all of these devices and all of them give me 'incorrect password'.

This admin password I gave is the one from my modem and is saved in my lastpass and chrome passwords, so I'm very sure that I've not simply misremembered it. I've tried retrieving it from all 3 places, so I'm sure I am entering the correct password.

What could be going on here? My own suspicions were that it might be one of the following:

I set the admin password incorrectly on a device, which then syndicated itself throughout the network so now all have an unknown admin password. (unlikely, as I tested all as working recently and after all devices were installed.)

One device malfunctioned and did this, then syndicated itself throughout the system.
Someone broke in and changed them (very unlikely)

I've tried using password 'admin'

Unfortunately tp link id is not set up so i can't access another way and see what the password is set to

I'd like to understand this before I reset the router, wifi/internet is currently still working

Does anyone have any ideas as to what might have happened?