nginx ifttt maker

Hi

I'm running node-red on a server at home. On an other server I'm running nginx. I'm trying to setup nginx as a reverse proxy and use ifttt maker to access an API provided by the node-red server. When I'm using postman or an other client, I can access the url without any problem:
178.197.233.28 - - [22/Dec/2016:23:10:40 +0100] "PUT /ifttt/ HTTP/1.1" 200 0 "-" "HTTPea/1.1.1 CFNetwork/808.2.16 Darwin/16.3.0" "-"

But when I try to access it over ifttt I'm getting always an error and I can see the following error in the log:
54.164.82.62 - - [22/Dec/2016:23:10:16 +0100] "PUT /ifttt/ HTTP/1.1" 400 951 "-" "-" "-"

The config for ifttt in nginx is very simple, in the /etc/nginx/conf.d folder I have a file with the following config:
server {
listen 80;
server_name ifttt.noesberger.li;

location /ifttt/ {
proxy_pass http://192.168.1.214:1880/ifttt;
}
}

Can you please help me to find the issue?