Custom Developer Visual is empty, but when uploading package it works

[Anonymous]

Hi Folks

In a previous post , I asked how to customize an existing Power BI. 

First I had problems compiling the whole project. But with the help of this Community I was able to compile the project, after I downgraded.

But now I have another problem. I can't see anything when using the Developer Visual. Even if I insert the right fields nothing happens.

But when I package the Visual and upload it, it works fine.

What could be the problem of this?

Edit: There are no errors in any Browser console

Thanks in advance

Hekuran