It is hard to tell from what you write if it is Animation Paper it self that is not loading (aka starting up) or it is your animation that is not loading into Animation Paper.
If it is the latter, please send me your animation file (.ap file), so I can investigate and check if it loads into Animation Paper here at my end. Please send it to my email, which is the one you got your activation key from. Use wetransfer.com or some other method if your file is large.
Thanks,
Niels