Activation Email not working.

Common issue with BuddyPress sites. Here's what we recommend : 

1. Install a third party plugin WP MAIL SMTP : https://wordpress.org/plugins/wp-mail-smtp/

2. Setup SendinBlue ( Free account gives you daily 300 emails ) sendinblue.com

3. Setup WP Mail SMTP with sendinblue api key

4. Install the plugin Vibe WP BP Mail fix : https://wordpress.org/plugins/vibe-buddypress-to-wp-mail-fix/

note : We use the same in our demos and test sites. Works flawless.