Outlook 365 not receiving email due to many reasons like- network connection problem or incoming email blocked by system firewall. Below Steps are very helpful when Outlook 365 won't receive new emails:-
1. In Outlook 365, Check the Spam Folder 2. clear cache 3. Overview Outlook Rules 4. Offline Mode disabled 5. Email Sorting Options Changed.
Closeout of the web browser completely and re-open it. Then sign back into your email account.
Sign out of your email account and sign back in again to re-authenticate with Duo.
Hit the web browser's "refresh" button, which is usually on the top of the window and usually looks like a curving arrow.
Clear your web browser's "all-time" history, cache, and cookies.
Try accessing your email with a private/incognito window.
Check your inbox and sweep rules within your settings.
Check your recycle bin or deleted inbox.
Check your spam, junk, and/or other possible inboxes/folders.
Check to see if you are blocking email addresses within your settings.
Check to see if you accidentally have auto-forwarding set up.
Search for the emails that you may be missing with the search bar to see if they are ending up in a different folder.
Check your network connection on your device.
Check for any web browser updates on your device.
Reinstall web browsers onto your device to ensure that you have the most updated ones.
Check to see if your computer/device has any pending or important updates to run overall.
Restart your computer/device.
Regards, Caleb