File password
For the latest versions of Quicken (2006 through 2020), the "file open" password cannot be recovered instantly. The only way to recover the password is trying the possible password combinations. This process is called an "attack". The simplest attack is brute-force, which tries all possible password combination within a given character set and of a given length. The program also supports complex attacks, like the Dictionary attack with mutations or the Mask attack. Please read this document to learn more about attacks.
After opening the file, select the attack and specify the options, then press the Start button to run the attack. You also can select which CPU and GPU devices are used for password recovery using the "Device manager" button. The attack can be stopped at any time with the Stop button.
Notes
The program has been tested with all US versions of Quicken as well as some German, Canadian, Australian, New Zealand and Spanish versions. Support for non-US versions is not guaranteed.