PO sets this combination of moves in Raichu as illegal while both moves can be obtained through breeding (event Pichu + another Pichu). This set in particular was used by the VGC 2016 Worlds Champion Wolfey
Try updating your client (the most recent version should be 2.6.2.1). Just re-download the client and install it
Yes, I did it and I worked. I didn't know of this updated version. Please delete this thread if possible, and thank you for your attention