Cannot login with Any email on Macbooks Apple ID

I am part of my companies IT support, We are in the process of reclaiming all our domain emails as managed apple ID's, to help users, I have one to ones with them to help them transfer the data of already in use business emails so they can be released and then converted to a managed ID.(process- login to https://appleid.apple.com/sign-in, transfer using an email I have created, signing out of the device and then signing in to their laptops apple ID with the now federated email)

This side of the process although troublesome, does work, however after successfully helping 20 users convert to a managed ID, I have 2 users so far (I have paused the process while I figure this out) that when they try and login with ANY email, either a managed or unmanaged even personal email they get "Verification failed" or "authentication failed" doesn't even ask for a password for the unmanaged accounts.

I have gone through most tips i've found on the web, restarting, closing all apps, signing out of everything, changing time and date, restarting routers, disabling VPNs, deleting keychain data, deleting icloud account folder, Nothing works.

Ive asked users to create a separate user on their macbooks and then trying to login, and that works on both.

It's not making any sense, I can also login on my mac with any of the users.

This is causing a big disturbance for us as a business as its now preventing these users from login in even with apple developer accounts.

Apple support are basically pushing the fault to google, our identity provider, but that for me is impossible as clearly the login is working using another laptop user.

Any help would be appreciated, as clearly apple support don't really know what is happening.

I need to avoid reseting the hole laptop as the users have far too much set-up to go through to enable their development work.

Devices: MacBook Pro (14-inch, 2021)

OS: 14.3.1 (Build 23D60) updated machines to this as the previous isntaled OS had same issue

Regards