Countdown is not a function

Enabling the Countdown Timer for the Coming Soon Mode page does not work on the homepage. It shows the timer, but only zeros are in its place.
( 00 ) ( 00 ) ( 00 ) ( 00 )

No plugins installed.
And the error on a browser inspector is

(index):88 Uncaught TypeError: jQuery(...).countdown is not a function
    at HTMLDocument.<anonymous> ((index):88)
    at i (jquery.js?ver=1.12.4-wp:2)
    at Object.fireWith [as resolveWith] (jquery.js?ver=1.12.4-wp:2)
    at Function.ready (jquery.js?ver=1.12.4-wp:2)
    at HTMLDocument.J (jquery.js?ver=1.12.4-wp:2)