After searching up what in the bloody hell Joiplay is and then doing some research. I found that the current version of Joiplay is only compatible with games created with up to version 8.13 of renpy. Succubus Kingdom is created on renpy 8.20 so that's why it doesn't work.
Sadly, nothing I can do to help you there friend, You will just have to wait until the 8.20 version of Joiplay is released and then it will work.