Using a Gen 8.6 Windows Oracle CSE the message "MDEXI0084E Cannot connect to MD at this time. Try later." appears when trying to run any CSE Clients which were previously connecting successfully to the CSE.

The CSE Service CSESvcMD is running and so is the Oracle Service for the Database Instance that it depends on. The Oracle TNS Listener Service is also running

Diagnostics:

a.  Using Windows Task Manager/Details tab check for CSE background server processes with names srv*. Normally 7 background servers are started when the CSE Server starts per this example:

One of those servers srvlock.exe has no DB connection, while the other 6 servers do. If only srvlock.exe is visible in the Task Manager that indicates the CSE failed to successfully connect to the Oracle Database for the other 6 servers.

b. From command prompt run: netstat -na|find "2500"

The output only shows 1 socket being used to the iefmd listening port 2500 i.e.

  TCP 0.0.0.0:2500 0.0.0.0:0 LISTENING

  TCP [::]:2500 [::]:0 LISTENING

  TCP [##.##.#.#]:2500 [##.##.#.#]:53198 ESTABLISHED

  TCP [##.##.#.#]:53198 [##.##.#.#]:2500 ESTABLISHED

Normally for the 7 CSE background server processes there should be 14 ESTABLISHED lines output above. Only seeing 2 ESTABLISHED lines corresponds to only the srvlock.exe process running.

c. From command prompt cd to the directory containing the iefmd.ini file and run CSE manually using command:  
"%GEN86%\cse\bin\iefmd" /mdini=.\iefmd.ini /mderr="C:\ProgramData\CA\Gen 8.6\logs\CSE\iefmd.log" 2>&1
The Coordination Server crashes with this event logged in the Windows Event Viewer > Windows Logs > Application:
Faulting application name: srvcoord.exe, version: 8.6.0.333, time stamp: 0x574c9284
Faulting module name: ntdll.dll, version: 6.2.9200.22601, time stamp: 0x5be76b3c
Exception code: 0xc000007b
Fault offset: 0x000683ba
Faulting process id: 0x15f8
Faulting application start time: 0x01d504bb9d5b2c41
Faulting application path: C:\Program Files (x86)\CA\Gen86\CSE\bin\srvcoord.exe
Faulting module path: C:\Windows\SYSTEM32\ntdll.dll
Report Id: db3753ca-70ae-11e9-941e-0200b7e70aa8
Faulting package full name: 
Faulting package-relative application ID:  

The Gen Windows/Oracle CSE is 32-bit software and requires the 32-bit Oracle 12c client to be installed. The Oracle 12c 32-bit client installation bin directory also needs to be in the System PATH before the 64-bit Oracle database server installation bin directory.

In this case after checking the PATH it was found that only the 64-bit Oracle database server installation bin directory was present and the Oracle 12c 32-bit client installation bin directory required by the CSE software was no longer present.

Locate the Oracle 32-bit client directory on the server and add it's bin directory to the front of the System PATH variable under "Control Panel/System/Advanced system settings/Environment Variables".  That ensures that the 32-bit version of the Oracle 12c client dll ORASQL12.DLL is picked up by the CSE software.

Start the CSE service CSESvcMD and use the Windows Task Manager to confirm that the 7 CSE background server processes are started. 

Once confirmed the CSE Client connection to the CSE Server should be successful.

Gen™ 8.6 > Technical Requirements > Development Platform Environments - see CSE & Host Encyclopedia