If I may.
Since yesterday everything was working, today stopped to work.
But template php code yesterday was this same as it today, right. It means that it may be a server file caching (or htaccess cache etc.), not template code problem. Becuase custom.css file is loaded every single time.
Above tip from @blue_Shift link helps - but .... it may be this same after "problem" you made changes after few minutes. That's why on localhost where is not extra caching changes are visible on the fly.
BTW
@blue_Shift thanks for sharing my tip :)