Mac won't save wifi password

Open system preferences > click on network ,if you are the administrator , enter your admin name & password to open the pad lock .

Keep the settings : location as Automatic , click on advanced > Wi - fi check the box of remember network this computer has joined , security as WPA2 personal AES , DNS settings as 8.8.8.8 and 8.8.4.4 , no proxies must be enabled , finally click on apply .

Regarding keychain , when you open safari & its preferences > click on auto fill , check all options so that when ever you login , your web mail , admin name passwords get automatically filled up in the keychain .

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If you know your old password, use that password to update your existing login keychain:

1. Open the Keychain Access app, which is in the the Utilities folder of your Applications folder.
2. From the Edit menu, choose “Change Password for Keychain 'login.'”
3. Enter the old password of your user account in the Current Password field. This is the password you were using before the password was reset.
4. Enter the new password of your user account in the New Password field. This is the password you're now using to log in to your Mac. Enter the same password in the Verify field.
5. Click OK when done, then quit Keychain Access.

As per this article : If your Mac keeps asking for the login keychain password - Apple Support