If you can’t save a password in Safari on Mac
You can use AutoFill to remember the passwords you enter for websites, then easily fill in the saved information when you revisit the same websites. If you can’t save your password for a website, try these suggestions.
Make sure AutoFill is turned on: Choose Safari > Preferences, click AutoFill, then make sure “User names and passwords” is selected.
Remove the “never saved” status: If you chose to never save the password for this website (by clicking Never in the dialog that appeared when you first signed in to it), your password can’t be saved until you remove that status. Choose Safari > Preferences, then click Passwords. In the list, select the website (“never saved” should appear next to it), then click Remove.
Contact the website’s administrator: Ask if the website allows passwords to be saved.