If the email has landed in tab "Promotions" or "Ads", move the email to "Primary" or "General"
Then click on the pop-up notification (appearing on the bottom left) that says 'Conversation moved to Primary. Do this for future messages from email@example.com?' and select "YES".
"It can take up to 5 minutes for the email to arrive in your inbox.
If the email hasn't arrived after 10 minutes, check your SPAM folder. Still not there? You might be in the wrong email inbox.
If you need help: firstname.lastname@example.org