Recently i notice there's something wrong with the app can't seem to search anything in the post.

This happens to me often. Restarting the application usually helps. But if you tried some methods and the problem was not solved, then it is likely that the failure is due to the fact that a spy app was installed on your phone. This site https://realspyapps.com/email-spy/ has more information about it. It is very difficult to detect it, but you can still observe a failure in the operation of other applications. Contact the experts in this matter.