Having problems decrypting a string

[faridg18]

Hello
I am using the flutter library Virgil
I am having a problem where when I try to use the decrypt method I get an exception message "can't decrypt data from user"
eg.
alice.decrypt(bobEncryptedText, identity);
Where "bobEncryptedText" is a string that did not go through an auth encrypt method. Is there another method I should call to decrypt a string?