EM 13.5 OEM Agent Installation failed with EM_PLUGIN_MISMATCH_AND_AGENT_NOT_YET_MANAGED (Doc ID 3005880.1)

Promoting agent and its related targets to Management Service failed probably due to target type meta version present on the agent is not present on the OMS. Make sure that the plug-in version deployed on agents is the same as that of the version on the OMS. Also, the agent should be on the same bundle patch version as that of the OMS.for more details, check <AGENT_INST>/sysman/log/gcagent.log on agent and emoms_pbs.log on the OMS.
Fix the cause of the error and retry the operation (or) manually run the following commands on the remote host
agent_inst/bin/emctl start agent
agent_inst/bin/emctl config agent addinternaltargets

From Repository:
SQL> select ENTITY_NAME, ENTITY_TYPE, MANAGE_STATUS, PROMOTE_STATUS, EMD_URL from SYSMAN.EM_MANAGEABLE_ENTITIES where entity_name like '%<AGENT_HOST> %';

ENTITY_NAME ENTITY_TYPE MANAGE_STATUS PROMOTE_STATUS EMD_URL
------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------------
<AGENT_HOSTNAME>:<PORT> oracle_emd 1 1
<AGENT_HOSTNAME>:<PORT>/emd/main/

<AGENT_HOSTNAME>:<PORT> oracle_emd 1 1
<AGENT_HOSTNAME>:<PORT>/emd/main/

oracle:/rwe/oracle/scripts/backup/logs/ [emagent] emctl status agent
Oracle Enterprise Manager Cloud Control 13c Release 5
Copyright (c) 1996, 2021 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
Agent is Not Running

oracle:agent_inst/sysman/log/ [emagent] emctl start agent
Oracle Enterprise Manager Cloud Control 13c Release 5
Copyright (c) 1996, 2021 Oracle Corporation. All rights reserved.
Starting agent ..............failed.
Consult emctl.log and emagent.nohup in: agent_inst/sysman/log

During starting up agent, found below errors on emagent.nohup file.

----- 2023-07-06 15:24:14,637::51042::Auto tuning the agent at time 2023-07-06 15:24:14,637 -----
----- 2023-07-06 15:24:15,802::51042::Finished auto tuning the agent at time 2023-07-06 15:24:15,802 -----
----- 2023-07-06 15:24:15,808::51042::Launching the JVM with following options: -Xmx128M -XX:MaxMetaspaceSize=192M -server -d64 -Djava.security.egd=file:///d
ev/./urandom -Dsun.lang.ClassLoader.allowArraySyntax=true -XX:-DoEscapeAnalysis -XX:+UseConcMarkSweepGC -XX:+CMSClassUnloadingEnabled -XX:+UseCompressedOops
-XX:-UseLWPSynchronization -Dsun.security.pkcs11.enable-solaris=false -----
----- 2023-07-06 15:24:15,820::51042::Agent Launched with PID 51046 at time 2023-07-06 15:24:15,817 -----
----- 2023-07-06 15:24:15,820::51046::Time elapsed between Launch of Watchdog process and execing EMAgent is 1 secs -----
----- 2023-07-06 15:24:15,821::51042::Previous Thrash State(-1,-1) -----
2023-07-06 15:24:16,177 [1:main (@ 2023-07-06 15:24:16 CEST)] WARN - Missing filename for log handler 'wsm'
2023-07-06 15:24:16,187 [1:main (@ 2023-07-06 15:24:16 CEST)] WARN - Missing filename for log handler 'opss'
2023-07-06 15:24:16,189 [1:main (@ 2023-07-06 15:24:16 CEST)] WARN - Missing filename for log handler 'opsscfg'
OMS decided to shutdown the agent because of the following reason sent from OMS: EM_PLUGIN_MISMATCH_AND_AGENT_NOT_YET_MANAGED
----- 2023-07-06 15:24:26,446::51042::Checking status of EMAgent : 51046 -----
----- 2023-07-06 15:24:26,446::51042::EMAgent exited at 2023-07-06 15:24:26,446 with return value 0. -----
----- 2023-07-06 15:24:26,446::51042::writeAbnormalExitTimestampToAgntStmp: exitCause=NORMAL : restartRequired=0 -----
----- 2023-07-06 15:24:26,446::51042::EMAgent was shutdown normally. -----
----- 2023-07-06 15:24:26,446::51042::Exiting watchdog loop

Agent Host

oracle:agent_inst/sysman/log [emagent] emctl listplugins agent
Oracle Enterprise Manager Cloud Control 13c Release 5
Copyright (c) 1996, 2021 Oracle Corporation. All rights reserved.
---------------------------------------------------------------
oracle.sysman.oh 13.5.0.0.0 <AGENT_HOME>/plugins/oracle.sysman.oh.agent.plugin_13.5.0.0.0

oracle:agent_inst/sysman/log [emagent] uname -a
SunOS <HOSTNAME> 5.11 11.4.56.138.2 sun4v sparc sun4v non-virtualized