|contact the vendor of the program.|
If it operates anything like the Etax software used in my country, the password required to open a .tax file is the tax file number. ( maybe your Social Security number if that is what is used where you are)
For some time my Gmail account was being spammed by something purporting to be about my turbo-tax lodgement. Until that appeared in my inbox I had never heard of the prog. Blew it away without opening anything.
Goin' Fishin' (Some day)