TeamCity Agent error: Error while asking server for the communication protocols

Hello JetBrains Team!

VPS: Ubuntu 20.04.2 LTS
Docker v20.10.7
Docker-Compose v1.29.1

I have the installed Nginx Proxy and Lets Encrypt. They allow to me to use HTTPS and unical URL address for each my container. It works fine. Now I want to start in the docker containers TeamCity Server and TeamCity Agent (through compose-file). My TeamCity Server works fine: you can see it on https://teamcity-server.dev.admincad.ru/

But TeamCity Agent doesn't work (its URL is https://teamcity-agent.dev.admincad.ru/ ). I get the error:

[2021-07-31 21:12:31,040] WARN - buildServer.AGENT.registration - Error while asking server for the communication protocols via URL https://teamcity-server.dev.admincad.ru/app/agents/protocols. Will try later: javax.net.ssl.SSLHandshakeException: PKIX path building failed: sun.security.provider.certpath.SunCertPathBuilderException: unable to find valid certification path to requested target (enable debug to see stacktrace)
[2021-07-31 21:12:31,041] WARN - buildServer.AGENT.registration - Error registering on the server via URL https://teamcity-server.dev.admincad.ru. Will continue repeating connection attempts.

In the web page https://teamcity-server.dev.admincad.ru/app/agents/protocols I see this:

<list><string>polling</string></list>

At this case I try to do it in my DEV environmen therefore for my Nginx Proxy and Lets Encrypt containers I use:

ACME_CA_URI=https://acme-staging-v02.api.letsencrypt.org/directory
LETSENCRYPT_TEST=true

Later (if all will work fine) I will be deploy it to PROD with such values:

ACME_CA_URI=https://acme-v02.api.letsencrypt.org/directory
LETSENCRYPT_TEST=false

This is my compose file (stack.yml) for TeamCity Server with TeamCity Agent:

version: "3.8"
services:
    teamcity-server:
        image: jetbrains/teamcity-server
        container_name: "${TARGET_ENVIRONMENT}_${COMPOSE_PROJECT_NAME}-server"
        restart: unless-stopped
        volumes:
            - "datadir:/data/teamcity_server/datadir"
            - "logs:/opt/teamcity/logs"
        env_file:
            - "../../common.env"
            - "../../common.$TARGET_ENVIRONMENT.env"
        environment:
            VIRTUAL_PORT: "8111"
            VIRTUAL_HOST: "${COMPOSE_PROJECT_NAME}-server.$HOST_URL"
            LETSENCRYPT_HOST: "${COMPOSE_PROJECT_NAME}-server.$HOST_URL"
            LETSENCRYPT_EMAIL: "$LETSENCRYPT_EMAIL"

    teamcity-agent:
        image: jetbrains/teamcity-agent
        container_name: "${TARGET_ENVIRONMENT}_${COMPOSE_PROJECT_NAME}-agent"
        restart: unless-stopped
        volumes:
            - "conf:/data/teamcity_agent/conf"
        env_file:
            - "../../common.env"
            - "../../common.$TARGET_ENVIRONMENT.env"
        environment:
            SERVER_URL: "https://${COMPOSE_PROJECT_NAME}-server.$HOST_URL"
            VIRTUAL_PORT: "9090"
            VIRTUAL_HOST: "${COMPOSE_PROJECT_NAME}-agent.$HOST_URL"
            LETSENCRYPT_HOST: "${COMPOSE_PROJECT_NAME}-agent.$HOST_URL"
            LETSENCRYPT_EMAIL: "$LETSENCRYPT_EMAIL"
        depends_on:
            - teamcity-server

volumes:
    datadir:
        name: "${TARGET_ENVIRONMENT}-server_datadir"
    logs:
        name: "${TARGET_ENVIRONMENT}-server_logs"
    conf:
        name: "${TARGET_ENVIRONMENT}-agent_conf"

networks:
    default:
        external: true
        name: "${TARGET_ENVIRONMENT}_proxy-network"

How can I solve the problem?

Thank you!