MSPC doesn't work. Doesn't show anything in the tabs. I noticed it gives a javascript error. Any way to fix this? Thanks!

/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2 jQuery.Deferred exception: t.size is not a function TypeError: t.size is not a function

    at HTMLSelectElement.<anonymous> (https://toet.store/wp-content/plugins/multistep-product-configurator/js/multistep-product-configurator.min.js?ver=1.2.4:1:1381)

    at Function.each (https://toet.store/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2:2976)

    at S.fn.init.each (https://toet.store/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2:1454)

    at HTMLDocument.<anonymous> (https://toet.store/wp-content/plugins/multistep-product-configurator/js/multistep-product-configurator.min.js?ver=1.2.4:1:1245)

    at e (https://toet.store/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2:30005)

    at t (https://toet.store/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2:30307) undefined

S.Deferred.exceptionHook @ /wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2

/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2 Uncaught TypeError: t.size is not a function

    at HTMLSelectElement.<anonymous> (/wp-content/plugins/multistep-product-configurator/js/multistep-product-configurator.min.js?ver=1.2.4:1)

    at Function.each (/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2)

    at S.fn.init.each (/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2)

    at HTMLDocument.<anonymous> (/wp-content/plugins/multistep-product-configurator/js/multistep-product-configurator.min.js?ver=1.2.4:1)

    at e (/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2)

    at t (/wp-includes/js/jquery/jquery.min.js?ver=3.5.1:2)