PNG LOGO WON'T SHOW IN PORTFOLIO

Hey community, 

I have a very upsetting problem. I recently created a portfolio and made some tries with different png logos I designed in photoshop. I also had a gif variation for when the mouse goes over it and it worked out very smoothly.

Nevertheless, for the past 2 days when I tried to change the logo it won't show on top of my page. I can see in the image case that it's loaded and I can resize/crop it, but it just doesn't appear on my portfolio. I tried many different sizes and formats but it's just invisible. I circled the place where it's supposed to appear. Text logos are working fine tho...

Has anyone ever had this issue ? 

Tell me if more infos are needed, but I hope there is a solution to my problem... 

Kisses from france !