Since you tried all the steps i would suggest you to create a Service Request to replace the Management module. I have come across couple of situation like this.    Also one more thing CX4 series with FLARE Release 29 EMCRemote has been replaced with RemotelyAnywhere (RA). To use RA you should enable remotely anywhere from the setup page and you need add your management workstation IP address to use this. Once you add your IP later on you can go to SPA IP:9519 and it will prompt you to enter your windows login credentials. Once you login with your windows credentials you will be able to login to SPA or SPB.   Refer Primus emc229035 & emc221553
I have a CX4-960 running flare 28 patch 19.  For the past 2 days, neither SP will serve up Navisphere and I can't get to the [URL] page to restart the mgmt server.  I am able to ping both SPs.  When I'm connected to EMCREMOTE and run navicli commands I get a message "Error returned from Agent - Agent not running".  I reseated the management module which didn't help.  I used EMCREMOTE to logon to each SP and can ping the localhost and the service LAN IP - 128.221.1.250.  We tried to terminate navicimom from the console of the SP but could not stop the thread.  This morning, I scheduled a rolling reboot of the SPs.  I rebooted SPB (removed and reseated) but the SP came back up still experiencing the same issue.  During the SP reboot, I logged onto some attached hosts and verified that the default LUN owners shifted to SPA and back to SPB after the reboot so I assume that the SPs are otherwise functioning properly.  Any ideas?
Both service processors responding to ping but not cli or web requests