since this is ODA related, I would create an SR, since this should not happen.
A workaround probably is pretty easy, but not recommended as this is ODA.
You can call asmca manually (as User Oracle and having an x-term anyhwere).
But since it already created the volume, probably what is missing is the ACFS format (mkfs -t acfs /dev/asm/<volname>)
And the mount command. It could also be that ODA registers the filesystem with (srvctl add filesystem).
Additionally I'll include your workaround/troubleshooting suggestions in the SR as they may prove helpful.
It's interesting that the volume was "created successfully" (via some shell based os command/utility?) whereas the next "idle instance" message indicates the script was possibly trying to perform a query or update when it failed/aborted.
I might make some time to check the /opt/oracle/oak/onecmd/tmp/asmcacreatevol.sh script to confirm my guesses.
Regardless you've answered my question, even if it does not solve the problem.