AxCrypt 1.x and 2.x are compatible in the sense that 2.x can open all files secured with 1.x. In addition to that, 2.x implements of lot of new rich features, while some functions of 1.x are deprecated. Files secured with AxCrypt 2.x are not possible to open with AxCrypt 1.x.
Please note: You cannot have both AxCrypt 1.x and 2.x installed at the same time.
Still, you can open/decrypt the old encrypted files with the original file password(which was used in the file encryption process).
If the above does not help,please provide more information about the issue and write a mail to firstname.lastname@example.org . you can send a screenshot showing where the problem is, it often helps us understand.