I started the process of migrating from my App Store purchase to the AgileBits download on my MacBook. With 1P 6.8.4, when I try to sync, the computer automatically switches to Safari I am prompted to enter my Apple ID and password. The first time I entered my password, I received the 'incorrect password' message. I then went to iCloud on the web and it also told me that my password was incorrect. This is despite using the very same password earlier in the day. I then changed my Apple ID password on my iPhone successfully. When I went back to 1P and tried to sync to iCloud, I was sent to the same webpage as before that prompted me to enter my AppleID password. I entered the new (verified) password and got the incorrect password warning again. I then went back to iCloud.com and that also told me that this new password was incorrect. (I had just verified that very same password by logging in and out of iCloud successfully). I have heard that resetting the password too frequently can flag security issues at Apple resulting in extended downtime. The app store purchase of 1P was made with the very same password that I was trying initially.
1Password Version: 6.8.4
Extension Version: Not Provided
OS Version: 10.13.1
Sync Type: iCloud