moreover you have configured candidate disks using /etc/init.d/oracleasm and listdisks command showing the disk.
bash-3.2$ /etc/init.d/oracleasm listdisks
Then follow my steps that may help:
1. Click “Change Disk Discovery Path” button
2. Enter the path /dev/oracleasm/disks and click OK
3. The picture should look like this:
That’s it. GOOD LUCK!