After OMS 13.4 Upgrade :Your browser sent a request that this server could not understand

Bad Request
Your browser sent a request that this server could not understand.
Additionally, a 400 Bad Request error was encountered while trying to use an ErrorDocument to handle the request.

$emcli login -username=sysman
Enter password

Error: Already logged in as user "SYSMAN". Use "emcli logout" to logout the current user.

$ emcli logout
Error: The connection to the OMS is broken or has been actively interrupted by the OMS (usually due to a communication timeout). Check the log files for further details

$emctl upload agent
Oracle Enterprise Manager Cloud Control 13c Release 3
Copyright (c) 1996, 2018 Oracle Corporation.  All rights reserved.
---------------------------------------------------------------
EMD upload error:full upload has failed: uploadXMLFiles skipped :: OMS version not checked yet. If this issue persists check trace files for ping to OMS related errors. (OMS_DOWN)

$ emctl secure agent
Oracle Enterprise Manager Cloud Control 13c Release 3
Copyright (c) 1996, 2018 Oracle Corporation. All rights reserved.
Agent successfully stopped... Done.
Securing agent... Started.
Enter Agent Registration Password :
Agent successfully restarted... Done.
Securing agent... Failed.

[13-09-2021 22:11:49] USERINFO ::Securing agent...   Started.
2021-09-13 22:12:04,154 [main] INFO  agent.SecureAgentCmd main.309 - emdWalletSrcUrl: https://oem_slb:4900/empbs/wallets/emd
2021-09-13 22:12:04,160 [main] INFO  agent.SecureAgentCmd secureAgent.392 - Querying HTTPS Upload Port of the OMS
2021-09-13 22:12:04,160 [main] INFO  agent.SecureAgentCmd openPage.987 - Opening: https://oem_slb:4900/empbs/genwallet
2021-09-13 22:12:04,457 [main] INFO  agent.SecureAgentCmd openPage.1014 - Response Status Code: 400
2021-09-13 22:12:04,458 [main] ERROR agent.SecureAgentCmd main.368 - Failed to secure the Agent:
java.lang.Exception: Didn't get a OK response from OMS
        at oracle.sysman.emctl.secure.agent.SecureAgentCmd.openPage(SecureAgentCmd.java:1017)
        at oracle.sysman.emctl.secure.agent.SecureAgentCmd.getOMSSecurePort(SecureAgentCmd.java:933)
        at oracle.sysman.emctl.secure.agent.SecureAgentCmd.secureAgent(SecureAgentCmd.java:393)
        at oracle.sysman.emctl.secure.agent.SecureAgentCmd.main(SecureAgentCmd.java:346)

[2021-09-13T22:24:28.4358+10:00] [OHS] [ERROR:32] [OH99999] [ossl] [client_id: xx.xx.xx.xx] [host_id: oms_host1] [host_addr: xx.xx.xx.xx] [pid: 30107] [tid: 140213158373120] [user: oracle] [VirtualHost: oem_slb:0] OHS:2079 Client SSL handshake error, nzos_Handshake returned 28860(server oem_slb:443)
[2021-09-13T22:24:28.4358+10:00] [OHS] [ERROR:32] [OH99999] [ossl] [host_id: oms_host1] [host_addr: xx.xx.xx.xx] [pid: 30107] [tid: 140213158373120] [user: oracle] [VirtualHost: oem_slb:0] OHS:2171 NZ Library Error: SSL fatal alert