I have a 2 node RAC (12cR2) machine that was running fine till a reboot of both the RAC nodes
My database unique name is "rac" and instance names are "rac1" and "rac2".
1) /oragrid/app/grid_home/bin/crsctl check crs
CRS-4638: Oracle High Availability Services is online
CRS-4535: Cannot communicate with Cluster Ready Services
CRS-4530: Communications failure contacting Cluster Synchronization Services daemon
CRS-4534: Cannot communicate with Event Manager
2) /oragrid/app/grid_home/bin/crsctl start res ora.crsd -init
CRS-2672: Attempting to start 'ora.gpnpd' on 'xxxxxxxxxx'
CRS-2674: Start of 'ora.gpnpd' on 'xxxxxxxxxx' failed
4) /oragrid/app/grid_home/bin/crsctl start cluster
CRS-2672: Attempting to start 'ora.gpnpd' on 'xxxxxxxx'
CRS-2674: Start of 'ora.gpnpd' on 'xxxxxxxx' failed