[theme: Pinbin] Can't upload logo

Please help, I can’t find how to fix this:

until some days ago I could upload the logo through the Theme Options, but now for some reason it doesn’t show the logo anymore (size is the same, png file, all seems ok),
I tried to upload with all the different options but it doesn’t work.
How can I put the picture in the header manually with the editor? Can you please enlighten me?

thank you