i just fixed this – had the same problem.
you need to open the file
jquery.nivo.css
it’s in the public_html/wp-content/themes/potassiumific/css folder
at the top of the page you’ll see the code:
#slideshow img {
position:absolute;
top:0px;
left:0px;
display:none;
}
you just need to change display:none to display:block and it should fix it.
you’ll need to access the file using FTP as it is not editable via the WP admin area.
Hope this helps!!