Hi I am also on Mac 6.1.1 via App Store and same problem - I enter the CORRECT decryption key but the encrypted text placeholder box is simply highlighted (blue) and not decrypted. Some notes will decrypt successfully, some will not. All have same decryption key. This is a serious, serious problem - I suspect many, many people rely on this feature for important information on a daily basis. Luckily I could still access the note via android app. Someone needs to seriously look into basic functionality testing for each release. I agree with the earlier comment - this seriously erodes trust.