Chirpstack sending zero bytes to ThingsBoard via HTTP

I’m having a problem sending over telemetry data to my ThingsBoard instance from the Chirpstack Application Server.

I’ve configured the Chirpstack integration to ThingsBoard. I also have an NGINX proxying HTTP traffic from port 80 and 443 to localhost:8080 (i.e. ThingsBoard).

What could I be missing?

NGINX logs:

X.X.X.X - - [23/Aug/2021:11:09:58 +0300] "POST /api/v1/iB9HJVYesb1dyIz3dvsV/attributes HTTP/1.1" 200 0 "-" "Go-http-client/1.1"
X.X.X.X - - [23/Aug/2021:11:09:58 +0300] "POST /api/v1/iB9HJVYesb1dyIz3dvsV/telemetry HTTP/1.1" 200 0 "-" "Go-http-client/1.1"
X.X.X.X - - [23/Aug/2021:11:10:13 +0300] "POST /api/v1/iB9HJVYesb1dyIz3dvsV/attributes HTTP/1.1" 200 0 "-" "Go-http-client/1.1"
X.X.X.X - - [23/Aug/2021:11:10:13 +0300] "POST /api/v1/iB9HJVYesb1dyIz3dvsV/telemetry HTTP/1.1" 200 0 "-" "Go-http-client/1.1"
X.X.X.X - - [23/Aug/2021:11:10:26 +0300] "POST /api/v1/iB9HJVYesb1dyIz3dvsV/attributes HTTP/1.1" 200 0 "-" "Go-http-client/1.1"
X.X.X.X - - [23/Aug/2021:11:10:26 +0300] "POST /api/v1/iB9HJVYesb1dyIz3dvsV/telemetry HTTP/1.1" 200 0 "-" "Go-http-client/1.1"

NGINX config:

server {
server_name thingsboard;
location / {
proxy_pass http://127.0.0.1:8080;
proxy_http_version 1.1;
proxy_set_header Host $host;
}
listen 443 ssl;
ssl_certificate /etc/ssl/certs/ssl-cert-snakeoil.pem;
ssl_certificate_key /etc/ssl/private/ssl-cert-snakeoil.key;
}

server {
server_name thingsboard;
location / {
proxy_pass http:/127.0.0.1:8080;
proxy_http_version 1.1;
proxy_set_header Host $host;
}
#location ~ ^/api.*$ {
# proxy_pass http:/127.0.0.1:8080;
# proxy_http_version 1.1;
# proxy_set_header Host $host;
#}
listen 80;
}