Can't add host server to cloudstack management server - brand new installation. #11140

problem

I did a fresh install and when I try to add the KVM virtualization hosts I get the following error message;
Unable to add the host: Cannot find the server resources at http://10.20.123.4

versions

CloudStack 4.20.1.0
OracleLinux R9 U6
Openjdk 17.0.15 2025-04-15 LTS
QEMU emulator version 9.1.0

The steps to reproduce the bug

1.I installed and updated the OS on the management server, I configured the bridges brcloud0 for management and brcloud1 for guest and public
2.I installed and updated the OS on the KVM Hosts servers, I configured the bridges brcloud0 for management and brcloud1 for guest and public
3.I tested connectivity between hosts via the management network using the FQDN
4. I accessed the management server through the GUI and created the zone, pod and cluster. Everything is OK, everything is enabled, no errors.
5. I click on the add host button, and fill in the information and try to add the host, that's when I get the error message
...

What to do about it?

I put all the logs in debug mode but I can't get a clue about the problem

----------------- LOGS FROM THE KVM HOST --------------------

[root@cshost02 ~]# tail -n 50 -f /var/log/cloudstack/agent/agent.log
2025-07-03 17:06:09,186 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [guid] has empty or null value. Using default value [null].
2025-07-03 17:06:09,187 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [developer] has empty or null value. Using default value [false].
2025-07-03 17:06:19,903 INFO [cloud.agent.AgentShell] (main:[]) (logid:) Agent started
2025-07-03 17:06:19,907 INFO [cloud.agent.AgentShell] (main:[]) (logid:) Implementation Version is 4.20.1.0
2025-07-03 17:06:19,909 INFO [cloud.agent.AgentShell] (main:[]) (logid:) agent.properties found at /etc/cloudstack/agent/agent.properties
2025-07-03 17:06:19,914 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [host] was altered. Now using the value [localhost].
2025-07-03 17:06:19,937 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [guid] has empty or null value. Using default value [null].
2025-07-03 17:06:19,937 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [developer] has empty or null value. Using default value [false].
2025-07-03 17:06:30,662 INFO [cloud.agent.AgentShell] (main:[]) (logid:) Agent started
2025-07-03 17:06:30,666 INFO [cloud.agent.AgentShell] (main:[]) (logid:) Implementation Version is 4.20.1.0
2025-07-03 17:06:30,667 INFO [cloud.agent.AgentShell] (main:[]) (logid:) agent.properties found at /etc/cloudstack/agent/agent.properties
2025-07-03 17:06:30,673 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [host] was altered. Now using the value [localhost].
2025-07-03 17:06:30,696 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [guid] has empty or null value. Using default value [null].
2025-07-03 17:06:30,696 DEBUG [agent.properties.AgentPropertiesFileHandler] (main:[]) (logid:) Property [developer] has empty or null value. Using default value [false].
2025-07-03 17:06:41,402 INFO [cloud.agent.AgentShell] (main:[]) (logid:) Agent started