Installation failed. Failed to receive heartbeat from agent on Centos 7.6

[#1]

I'm trying to install Cloudera Data Platform Data Center but in the step of Install Agent, I got this error:

Ensure that the host's hostname is configured properly.
Ensure that port 7182 is accessible on the Cloudera Manager Server (check firewall rules).
Ensure that ports 9000 and 9001 are not in use on the host being added.
Check agent logs in /var/log/cloudera-scm-agent/ on the host being added. (Some of the logs can be found in the installation details).
If Use TLS Encryption for Agents is enabled in Cloudera Manager (Administration -> Settings -> Security), ensure that /etc/cloudera-scm-agent/config.ini has use_tls=1 on the host being added. Restart the corresponding agent and click the Retry link here.

For the log file, I got this error:

>>SSLError: unknown protocol
>>[05/Mar/2020 09:12:39 +0000] 668 MainThread agent ERROR Heartbeating to 127.0.0.1:7182 failed.

[#2]

@Rah It's worth to check if you have TLS enabled installation. I see a note in doc which needs out attention.

If you have enabled Auto-TLS, you must include the Cloudera Manager server host when you specify hosts. 

https://docs.cloudera.com/cdpdc/7.0/installation/topics/cdpdc-install-runtime-using-wizard.html

Did you restart CM after disabling TLS? Also, when you are using the add host wizard, you do not want to set use_tls=1 until the host is successfully added. It is actually kind of a messy procedure:

1. Disable Use TLS Encryption for Agents, and Use TLS Authentication of Agents to Server.
2. Restart CM
3. Add host to CM
4. Turn on Use TLS Encryption for Agents, and Use TLS Authentication of Agents to Server.
5. Configure agent to use TLS (setting use_tls=1 and the cert/key parameters, or copy config.ini from another host with TLS enabled).
6. Restart agent

Alternatives:

• Use Auto-TLS introduced in C6
• Follow the "Alternate Method of installing Cloudera Manager Agent without Disabling TLS" steps instead.
  
  If above does not help then we need full log file from CM server to take a look.

Cheers,