Authentication dialogs to permit access to your keychain are supplied by the macOS security system, and follow a strict pattern.
keychain
This new version adds a Help Book, Tooltips, and supports window resizing more usefully.
Significant improvements to Consolation for browsing logs. The others gain proper version numbers and icons.
This may help you work out what is going wrong with local keychains in Sierra. Another free tool to spare you from Terminal.
Sometimes resorting to Terminal can be the best and simplest way to fix a keychain problem.
OS X used to provide a keychain first aid feature. Now this has gone, this is the only way that you can try to repair a defective keychain: create a new one.
When the password used to log in and that to unlock your login keychain become different, you may be asked to keep entering your keychain password. Here’s how to fix this, and more.
Late last year, the utility for repairing keychains quietly vanished from macOS 10.11.2. No one seems to know where its functionality went.
Why do I have to enter my keychain password every time my Mac starts or restarts?
Can I change password entry dialogs to show the correct characters instead of blobs?
The Eclectic Light Company 