“Preload cache” isn’t work

Hello,

I’m not sure if something is not working. Let’s see: when I click on “Preload cache now” the preload doesn’t excecute, it just show a message (about to wait 10 seconds) but when you refresh the page, appears the “Preaload cache now” button again.

If i check the cached files list in the content tab, is empty. I have to go to Preload tab and click the “Preaload cache now” button one more time. If I refresh the page (after 10 seconds), now i can see how pages are caching one by one until finish.

?Is it ok? I hope you can help me. Thank you!