Have to restart to make it work

Hi there, I’m using this plugin and it seems to work like it should. It’s just one thing, when I enter the site for the first time it doesn’t recognise the bigger version for retina. I have to refresh the page to get it to work. Do you know why this is and what I can do to fix it?

Thanks in advance,
G

https://www.ads-software.com/plugins/simple-wp-retina/