You have lost or forgotten your master password for Panda Password Manager.
If you forget your master password, you cannot open the corresponding password list anymore, as it is said when creating a file. There are no backdoors. You may try all variants of the password you may have used (upper and lower case), but if the password is not correct, the file will not open.
Not all the program is lost, but only the corresponding file. You should click on Cancel in the Master Password Dialog. Then, the program will open without any password file. Finally you can create a new password file via the main menu New.
Sometimes, a password file may get damaged if the computer breaks down while the program is open or similar. Password Depot automatically backs up your password list at:
(My) Documents\Password Depot\Backup.
You can restore your password list by opening the backup copy using your master password and saving it again. Open the program, go to the main menu and click Open. Now, click Browse and open the above mentioned path. Select the latest .bck file and then click Open. Confirm your selection with OK to get to the Master Password Dialog.
Afterwards save the backup copy as a .psw6 file again via the main menu Save as in the desired directory.