I think it would help if you could try and remember a few more details from the plot apart from that scene, which very likely (if it was just a brief scene and not crucial to the plot in any way) will not be mentioned in the synopsis of the film to be found online (and therefore selecting 'tennis' as one of the search parameters will probably be useless...
).
Do you remember for instance whether it was set in a city or in the countryside, what city/country, what class/social scene did the main characters belong to, do you remember any distinctive features or details about the characters, or other things that happened outside of this tennis game? Did they visit a rail station at one point? What did they do? They can't just have been sitting around watching tennis for the entire film- try thinking back and visualising the scene, if you try mentally picturing that scene in your head and ruminating on it, perhaps more of the plot or more visual clues from the story will come to you... ? (Sorry, just to clarify absolutely not trying to be mean/sarcastic or having a go, just trying to help- Although I'm not very good at it
x Good luck in your quest to find a solution to this- admittedly very mysterious- conundrum)