UPDATE VIBE COURSE MODULE PLUGIN TO VERSION 220.127.116.11
if you do not want to update ( no reason i can think of ) follow below :
This issue is in buddypress plugin itself and happens on wordpress default 2017 theme also /
Re-installing emails from wp-admin -> tools -> buddypress -> re-intall buddypress default emails does not imports the activation emails .
To import this email please download and extract the import file from zipped file given here : https://bit.ly/2GH7jpT
Then please goto wp-admin -> tools -> import -> choose wordpress importer -> upload file and run import .