Check if it's not in the spam folder of your email client? For Outlook, that would be https://outlook.office.com/mail/junkemail
Also, add the sender to the safe senders list. To do this, go to https://outlook.office.com/mail/ and refer to the attached screenshot on how to proceed. Open a previous email from the sender, click on the three dots on the right ①, then click on Block ②, and choose 'Never block' ③.