When users request to join a closed group, the group admin receives a notification email as follows:

Hi, (name of user)
COM_COMMUNITY_NEW_MEMBER_REQUESTED_TO_JOIN_GROUP_EMAIL

The constant is expected to translate into a string like this. But, fails to do so.
%1$s requested to join the group, %2$s To view the group, follow the link below: %3$s

Please help
R.