If any one else had a problem like that!

I tried to update OpenCore 0.6.4 to 0.7.3. I did everything as the guide told me and it wouldn't boot.

I was using an outdated ProperTree and I didn't know (I found it by accident) that you have to have the latest ProperTree too.

I downloaded the latest ProperTree and now it boots. I changed nothing else.

Or, was it just in my case?!