i purchased the engine but i can't download it at itch.io because it relink tu the buy site.

An easy 3D desktop Game Engine scriptable in Python. · By
Create an account to the website using the same email you have on itch here: https://uniday.studio/cave/onboarding and then, once logged, you should be able to download the engine here: https://uniday.studio/cave/download
This is necessary because our server will build a new Cave Engine specific for you. :)
Due to the amount of new users getting the engine right now, the server is having a hard time catching up. Please DM me in our website: https://uniday.studio/user/UnidayStudio and I'll manually confirm your purchase for you.