Slider not running

getting an error

(index):600 Uncaught TypeError: $(…).slick is not a function
at HTMLDocument.<anonymous> ((index):600)
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)

and page not working after an updating porto theme.
any pointers would be appreciated

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