Promtail error sending batch, will retry - context deadline exceeded

I have free tier of Grafana Cloud. I wanted to send logs to Loki by Promtail. This is my docker compose for Promtail:

version: "3"

services:
  promtail:
    image: grafana/promtail:2.5.0
    volumes:
      - /etc/promtail/config.yml:/etc/promtail/config.yml
      - /var/log/app:/app/logs
    command: -config.file=/etc/promtail/config.yml -config.expand-env=true

And this is my Promtail config file:

server:
  http_listen_port: 0
  grpc_listen_port: 0

positions:
  filename: /tmp/positions.yaml

client:
  url: https://<user>:<password>@logs-prod-eu-west-0.grafana.net/loki/api/v1/push

scrape_configs:
- job_name: system
  static_configs:
  - targets:
      - localhost
    labels:
      job: app
      __path__: /app/logs/*.log

If I run Promtail on server I am receiving errors:

2022-07-29T22:58:41.046124553Z level=warn ts=2022-07-29T22:58:41.045587747Z caller=client.go:349 component=client host=logs-prod-eu-west-0.grafana.net msg="error sending batch, will retry" status=-1 error="Post \"https://<user>:***@logs-prod-eu-west-0.grafana.net/loki/api/v1/push\": context deadline exceeded"

When I run it from localhost, it works (from container and by curl). If I run API with curl from server, it works. If I run Promtail with dry run mode from docker container, it works:

cat /app/logs/app.log | promtail --stdin --dry-run --client.url https://<user>:<password>@logs-prod-eu-west-0.grafana.net/loki/api/v1/push
Clients configured:
----------------------
url: https://:<user>:<password>@logs-prod-eu-west-0.grafana.net/loki/api/v1/push
batchwait: 1s
batchsize: 1048576
follow_redirects: false
backoff_config:
  min_period: 500ms
  max_period: 5m0s
  max_retries: 10
timeout: 10s
tenant_id: ""
stream_lag_labels: filename

level=info ts=2022-07-29T23:01:05.966685041Z caller=server.go:260 http=[::]:80 grpc=[::]:9095 msg="server listening on addresses"
level=info ts=2022-07-29T23:01:05.967562785Z caller=main.go:119 msg="Starting Promtail" version="(version=2.5.0, branch=HEAD, revision=2d9d0ee23)"
2022-07-29T23:01:05.968599967+0000	{hostname="a92fcdf485cd", job="stdin"}	2022-07-29 23:39:27,927 [INFO] No new posts founded.
2022-07-29T23:01:05.968606686+0000	{hostname="a92fcdf485cd", job="stdin"}	2022-07-29 23:39:27,928 [INFO] Script took: 0.18s.

I tried to set batchwait to 10s, it did not help. When I POST logs with curl, it works from localhost. I cannot test curl from inside the container because I cannot install curl.

It looks like problem is with docker but cannot determine why, on localhost, Promtail in docker works fine.

Getting the same errors. Any one has any hints for that?