Problem with ading products by integration

Hi,
I got problem with ading products with integration of other system.
In this system shows information:

{“code”:”rest_no_route”,”message”:”No route was found matching the URL and request method”,”data”:{“status”:404}}

This system support told me that it should be problem with my website and they send me this, but i dont know what can I do with this.
https://ww.wp.xz.cn/support/topic/no-route-was-found-matching-the-url-and-request-method-4/
Could you check it and help me?

If I change Jquery version by myself will i get support in future?

The page I need help with: [log in to see the link]