Even if you get the restore working, it could very well be the result won't work on your aunts PC, since it's a different PC. https://askleo.com/restoring-an-image-backup-from-one-computer-to-another/ explains.

You're doing it correctly.All https://www.pcmag.com/how-to/how-to-back-up-and-restore-an-image-file-of-windows-10 tells you have to do now is "follow the prompts in Windows to restore your image file."

So I assume the prompt you get is for a username and password. I don't know if that's normal. Better try to make a new image of your aunts PC to another external disk and see what happens if you restore that.

If it really is a username and password, I expect it should be a username and password valid for both that image and for the PC you run the recovery on. And it could be that it must be a local account and password, not a Microsoft account.

I've never had troubles to restore from an image made by Acronis. Neither the whole system (after booting from the rescue disk), nor individual files (after opening the image in Windows).
But, indeed, the Microsoft variant seems to be troublesome.

For later, remember the purpose of an image backup to overcome a serious issue (hard disk crash, OS ruined) on the same computer the image was made from. For all other purposes a simple file backup is much better, since it can be read on any other PC.