Try these in order for new Outlook on Windows:
- Check internet access.
- Open a browser and go to
http://www.microsoft.com or http://www.bing.com.
- If neither site opens, fix the network connection first.
- Force a manual sync.
- In Outlook, go to the View tab and select Sync.
- Watch for the status message at the bottom of the message list while Outlook syncs.
- Note: third-party accounts such as Gmail, Yahoo, iCloud, or generic POP/IMAP do not have the same manual Sync capability.
- Check for a stuck large message.
- Open the Outbox.
- Start with the oldest stuck message.
- If it has an attachment larger than 20 MB, remove it and resend with a smaller file or a link to the file.
- Large attachments can block that message and messages sent after it.
- If the password was changed recently, update it in new Outlook.
- Select the icon next to the email account name.
- In the pop-up, select Continue.
- Follow the prompts and enter the new password.
- If Outlook shows a message like Please create an app password for Outlook on your email provider's site:
- Go to the email provider and generate an app password.
- Copy that app password and paste it when Outlook asks for the account password.
- If Microsoft cloud storage is full, free up space.
- Full Microsoft cloud storage can prevent sending and receiving email.
- Check mailbox storage and remove items if needed.
Since test messages sent from Gmail to the Outlook account also are not arriving, focus first on internet connectivity, manual sync, password re-authentication, and storage.