Can't install Marketpress, can't upload to content folder

Hi there, I keep getting different errors when trying to install marketpress. The last error was:
Downloading install package from…

Unpacking the package…

Could not copy file. marketpress/ui/css/jquery-ui.min.css

I have deactivated all plugins and when still got an error, deleted plugins and then I got the error can't upload to wp-content folder.
Not sure what else I can try.