please check following things :
- first of we need to check if the server supports php mail function or not .The simplest way to check this is to check if the default wordpress wp-login forget password email is working or not ?
that screen appears from here :
http://prntscr.com/khbxn9
this uses wordpress core function which uses mail function .
2: Second thing is to check all emails templates are imported or not from wp-admin -> emails .There must be atleast more than 70 different emails in there .
if not then please follow :
https://wplms.io/support/knowledge-base/migrate-all-the-wplms-emails-to-buddypress-again/
3: try using this plugin :
https://wplms.io/support/knowledge-base/postman-smtp-for-emails/