a. SecureAccess only runs on the USB drive.
b. SecureAccess uses many things in determining it’s encryption algorithm.
c. If you want to reformat the drive, you need to backup the files inside the vault, not the vault.
d. Most drives larger than 32 GB I believe are formated as exFAT which supports files larger than 4 GB.
Maybe reformating the drive back to the format it was will help the vault files.
Maybe restoring the drive from the backkup you made before formating will help.
Keep us updated on what works for you.
