Search in Outlook stopped working for me. I type a name that I know is in my inbox and it says "We didn't find anything to show here". Outlook 365 on Windows 11, mailbox is about 12GB. Restarting did nothing.

This is almost always the Windows Search index, not your mailbox. Rebuild it.

1. Close Outlook.
2. Open Control Panel > Indexing Options > Advanced.
3. Click Rebuild under Troubleshooting. Windows warns that it can take a long time. That is normal.
4. Reopen Outlook and give it a few hours. Search results fill in while indexing continues.

You can watch the progress in Outlook. Click in the search box, then Search tab > Search Tools > Indexing Status. It tells you how many items are left.

Rebuilt it. Indexing Status says about 41,000 items left. Is there anything to check in the meantime?

Yes, two quick checks.

In Indexing Options click Modify and make sure Microsoft Outlook is ticked. If it is not, Outlook is not being indexed at all.

In Outlook go to File > Options > Search and check that you are not limited to "Current Folder" only. Also check the "Include results from only the current folder" box in the search scope. If you work in Cached Exchange Mode, search only covers the part of the mailbox that is cached, so move the "mail to keep offline" slider to All if you want to search everything.

It finished overnight and search works again. The scope setting was set to current folder as well. Thanks both.