keychain

Have you rebooted since changing those settings? If not then do the following: boot into Safe Mode according to How to use safe mode on your Mac and test to see if the problem persists. Reboot normally and test again.

NOTE 1: Safe Mode boot can take up to 3 - 5 minutes as it's doing the following; 

• Verifies your startup disk and attempts to repair directory issues, if needed

• Loads only required kernel extensions (prevents 3rd party kernel/extensions from loading)

• Prevents Startup Items and Login Items from opening automatically

• Disables user-installed fonts 

• Deletes font caches, kernel cache, and other system cache files

NOTE 2: if you have a wireless keyboard with rechargeable batteries connect it with its charging cable before booting into Safe Mode. This makes it act as a wired keyboard as will insure a successful boot into Safe Mode.

The Keychain is an encrypted privacy storage mechanism to hold all your secrets which includes passwords, certificates, secure notes, etc. There 2 keychains per user and a global System and System Roots Keychain.

The default macOS behavior is to unlock the keychain when you login to macOS. It should remain unlocked so long as you are logged on. But there are options to auto lock the keychain after a timeout or waking from sleep.

Open up the Keychain Access App. On the left sidebar you will see:

login <-- Your primary login keychain

iCloud <-- iCloud Keychain used to sync passwords between multiple devices

System <-- System Keychain which is global to all users

System Roots <-- System Root certificates

Does the 'login' keychain show it is locked or unlocked with the icon to the left of 'login'?

Right-click the login keychain and select Change Settings for Keychain login. Make sure it's not set to Lock after so many minutes of inactivity nor Lock when sleeping.

*** If your Mac is managed by your employer they might have set these options forcefully and they will appear greyed out (disabled) so you cannot change the settings.

You can also create additional keychains, perhaps you need to secure some special certificates and passphrases / passwords for high security needs. You can put those items in a custom keychain and configure it to auto-lock, etc.

Some sites have additional security measures. Such as this Discussions forum, when signing in, I am prompted to provide my Mac password before it will sign-on with my Apple ID. My Mac password is not the same as my AppleID. I can use my Apple Watch or TouchID to unlock as well. But sometimes I will have to input the password now and then.

Some websites use a variety of tricks to prevent you from saving the password and auto-filling it.

You are being prompted to use TouchID to allow the autofill. Scan your TouchID finger print and it should continue without the password. You can manually choose to enter the Mac password to allow it instead.

This is a security feature to prevent someone else walking up to your Mac and submitting your password. It's verifying your identity to allow the automatic username and password submission.

That's good news. 👍

Can you take a screenshot of the login prompt that is requesting your Mac password?