BuddyPress.org

Dear @inspirationacademy,
Unhide the .messages-form .submit (Astra Pro may be hiding it) with:
.messages-form .submit { display: inline-block !important; }
If it’s still missing, copy the BuddyPress messages template into your child theme, add back the <button type="submit" name="send">Send</button>, then clear all caches.