If the Outlook search function is not responding, then try to troubleshoot this issue by rebuilding Outlook search index. First of all, go to File and then select Options. After that, click on Search given on the left and then select Indexing Options. After that, choose the “Advanced” option. In the end, click on the Rebuild option. After this, your Outlook search not working problem will get resolved. If this does not help you out with your issue, then try updating Microsoft Office 2016.
https://prompthelp.us/blog/out....look-search-not-work