I am using windows 10 and ArcGIS 10.5. About 2 weeks ago, I noticed that I was unable to open tools from the search. For example, I would search for "buffer" in the search dialogue box - then I would click on it and nothing would happen. Similarly, I would try to drag the tool into model builder, it would seem like it was trying to populate in the model builder but never appear. Prior to this it worked fine.
Currently, I can navigate to the tool through the toolbox and open the tool successfully.