Hello,

Please replace the code with this one:

body .product-grid-item .price,
body .single-product-page .summary-inner > .price {
        font-size: 0;
}
.single-product-page .summary-inner > .price > .woocs_price_code > span:first-child {
   font-size: 22px;
}
.single-product-page .summary-inner > .price > .price .woocs_price_code > small {
    font-size: 18px;
    margin-left: 6px;
}
body .product-grid-item .price .woocs_price_code > ins,
body .product-grid-item .price .woocs_price_code > span:first-child {
   font-size: 14px;
}
body .product-grid-item .price .woocs_price_code > del {
    font-size: 12px;
    margin-right: 3px;
}
body .product-grid-item > .price .woocs_price_code > small {
    font-size: 12px;
    margin-left: 4px;
}
body .single-product-page .summary-inner > .price .woocs_price_code > ins,
body .single-product-page .summary-inner > .price .woocs_price_code > span:first-child {
   font-size: 22px;
}
body .single-product-page .summary-inner > .price .woocs_price_code del {
    font-size: 22px;
    margin-right: 6px;
}

Clean your cache. The price plugin you have was the reason the previous code did not work.

Best Regards