Hes right. The exact same thing happened to me (using dropbox as well). I even typed in the password on my phone, and copied it. I then submitted the password on the phone and it worked (so i know the copied password is the right password). I then emailed myself the copied password so i could copy it on my computer. I then pasted the password to enpass and it said wrong password, just like op. What i had to do to get it working was save the backup on my phone instead of the cloud, and attached it to an email i sent myself. The password then worked fine, and it is syncing with dropbox like it is supposed to. Really weird bug, but for anyone else experiencing this just follow what i did, and it will work.