Installation of Multi-Domains failed

I am trying to install your plugins but I get this: "Installation of Multi-Domains failed. Most likely reason for this are wrong folder permissions of your wp-contents folder."

I searched the Forum and I changed the permissions to 755 and tried also with 750 and 744 as it was suggested in many similar post. But it does not work in my case :disappointed:

I will be grateful for some help!

Best regards,

PS I granted you the access. Many thanks in advance!