WP-JSON / Rest Api

What other plugins and theme do you use on the site?

I was able to solve the problem. After a long search and comparison with working websites, the cause is very simple.
In the search form I had stored the class ‘wpcf7’ from CSS. This form has no ID compared to CF7 forms.

I assume that when CF7 renders, it looks for all forms with the class ‘wpcf7’ and passes the id in them to the Rest API.
In my case, the CF7 script doesn’t find an ID in the search form, that explains NaN.

After removing the ‘wpcf7’ class in the search form, everything works fine ??

Thanks for the best WP Plugin!!!

I have a similar problem, however I do not understand your solution.
After updating cf7 to the latest version, I have the same error, I put the form into the code as a shortcode, I didn’t change anything in the plugin’s source code, etc.

Search for all ‘wpcf7’ classes in the source code. If you find a ‘wpcf7’ class, that isn’t related to a cf7 form -> you have to remove it. That was the solution in my case.