I figured out where was the problem. We used to have 3.x.x version. Since version 3 does not come with ARS table, our vendor used short codes on the User Restriction applied to all lines. We lost the secondary dial tone if we do not remove those short codes. I have to work on those when I have a chance.
I guess the credit card machine was waiting for the secondary dial tone. Since it did not get the secondary dial tone, it quit processing.
Anyway, I would like to thank all of you for being there to help.