Safari.. Sign in bar no longer present on a business website but present on other browsers

About a year ago now, a specific business related website I log on to about once a month suddenly ceased to show a "sign in" button (on the Safari web browser) below the normal "username" and "password" fields... It previously worked fine for years on Safari and then one day I went to the URL and much to my surprise, there was a "username" and "password" area (field) in which to enter those parameters but NO SIGN IN BUTTON... That button still exists when using other browsers like Firefox or Google Chrome but not Safari. See attached a screenshot of the hard to miss button grabbed using Google Chrome... What feature or security add-on on whatever would have caused Safari to no longer present this button about, say, a year or so ago... Curious!!!!