Please search the right word and check the issue. If the issue remains, share the WP admin login details of your site so I will check and give you a possible solution? Also share the page url where you are using this widget.
Now I have visited your site edited the portfolio widget and selected the category. It is working fine.
Screenshot for clarification: https://ibb.co/HHFFLMB
Check back on your site after completely clearing the browser cache and selecting the categories.