These issues could have many different roots, and can be fixed by doing different things.
There are various degrees of malfunction you may have to contend with dealing with the Outlook Search Index: it can completely stop working and give you zero results it may show results up to a certain date or the Outlook Search Index will tell you that there are items that are still waiting to be indexed. When it stops working, it can seriously affect your ability to quickly navigate through your emails. Outlook search is arguably one of the most important tools on an email client.
There’s no need to worry though, there are things that will help you get your Outlook 2016 search up and running again.
Microsoft Outlook Search not working is an issue that is common across all versions because all of them have the same base on how it functions, and that is the Outlook Search Index. One of the most common issues that occur with most Outlook clients is the search tool not working as it should.