In this particular case, I am trying to read a secured string from a file made by another user. When such a file with a password is prepared without the –Key or –SecureKey parameters of ConvertTo-SecureString, only the same user account on the same computer will be able to use this encrypted string.

Source: https://www.pdq.com/blog/secure-password-with-powershell-encrypting-credentials-part-1/#convertto-securestring-encrypting-passwords-and-other-strings

A similar topic: ConvertTo-SecureString run without key on different user account, is there a way (with proper credentials) to get this working from a different user?