Plugin error with special characters

Hi, my website http://www.donacoelha.com uses the free version of YITH WooCommerce Ajax Search.
This is a brazilian site so, often we uses special characters like “ç”, “á”, “í”, “é”, “ã” and users are redirect to a Forbidden page.
Can you help?

This is a very important issue.

Thanks.

https://ww.wp.xz.cn/plugins/yith-woocommerce-ajax-search/