Doesn’t work

I had the free version, it worked for me without problem so I was encouraged to buy the pro version to be able to personalize my website. It doesn't work! Whenever I go to "Customize" it loads briefly, but then it gives me loading error. It doesn't happen to me with any other subject, not even with this one in free version. I have deleted all themes, I have installed only this ... Nothing works. I feel like I've thrown 59 euros... Help me, please!