[Brajesh Singh]

@sagelives Try deactivating and activating forum for the group again(from Group->admin->settings), sometime It happens, If it is not solved, please do provide errorlog

@supermario
It is not available in the wp-admin. Check the front end of your site. If you are using bp-default theme, you will see a group link in the top menu . Click on that and you will see options to create.