“wpcf7_unit_tag_not_found”, “There is no valid unit tag.”

Hello friends
I am using Nuxt as front-end, WordPress as back-end for CMS purpose. In front-end, I create a form-data below:
……
some code
….
body.append(“_wpcf7”, “20”);
body.append(“_wpcf7_version”, “5.9.8”);
body.append(“_wpcf7_unit_tag”, “wpcf7-f20-o1”);

My problem is that I receive the code “wpcf7_unit_tag_not_found” and message “There is no valid unit tag.” I check my form id and it is correct. I check my syntax and it is correct as well. However when I try out with Postman, magically, it works. Then I try out on WordPress theme, it works. I know it works because I receive the auto response email. The saddest things is it does not work when I use POST API call on Nuxt.

Can someone please help me out ?
Thank you so much in advance.!!!