At the start of Spider-Man: Far From Home May throws a banana at Peter which he fails to notice coming which hits him. She then states that his "Peter Tingle", Spidey sense, was not working.
This continues to be a theme through the film until the final battle in London. I don't remember much of an explanation given for why it wasn't working and why it all of a sudden started to work again. He does have a brief conversation with Happy but I believe that just amounts to him saying "yeah it works again".
So, why was his "Peter Tingle" not working and how did it start working again?