Maybe your files use md5 encpypted passwords.
Just change your register script, make it work with md5 encrypation and it should work fine.
Another way to test is going on a

and create a new md5 password, paste it on your zPasswd and try to enter. If none of this works, then it's wrong db/services/version or whatever.
Hope I helped you,
#StayVeri <3