you can enable the gr gloabally under routing-options hierarchy..
also, As Karan mentioned,
>show task replication >> check if protocol sync is completed
>request chassis routing-engine master switch check
Above two commands will tell you the exact state of the sync between Master and Backup RE and will give you go ahead if you can perform master switch or not..
Also, during the switchover next time, you might want to collect the log messages and chassisd logs to tell you the difference between working router and non working router as well.