Managed to solve it by reinstalling the VMGR component. Uninstall the ST9 STMediaServer component with the IIM and remove all the ST related directories and those from SOLIDDB.
See -> http://www-01.ibm.com/support/knowledgecenter/SSKTXQ_9.0.0/admin/install/inst_uninst_av_vmgr.dita
I got some warnings after reinstalling but was able to fix them by running a script ( updateVMgrTemplates.sh ) as mentioned in the details of summary screen of the installation.
AVKCS2200E: Failure response 500 -- when the VMCU is down or cannot be reached.
AVKCS2200E: Failure response 503 received in response to invitation -- when something ( probably ) is wrong with the default av.ConferenceDefaultTemplate template.