The most likely reason for this is that the files you can’t open now, you couldn’t open before either because they are in fact not encrypted with any of the passwords you’ve tried.
This is easy to demonstrate. First check the “last modified” date of the encrypted files in question. If this is *before* the upgrade to a new PC, they have not changed since.
You can now uninstall AxCrypt 2, re-install AxCrypt 1, and verify that the files in fact do not decrypt using the passwords you expect now either. If you’d like to avoid the inconvenience of uninstalling AxCrypt 2, you can use either AxDecrypt, or AxCrypt2Go which can be downloaded and run independently. All of the legacy version 1 software is available at the legacy web site, http://www.axantum.com/ .
If the above does not clarify the situation, please provide more information and screen shots.