child theme styles fourteen dont work

I have a site where I use and old theme called “dark” which I now wants to replace with “Twenty fourteen”. I have made a copy of my website and use this as a testpage for the new theme. It’s a mulitilingual site with two languages. I only changing theme on one of the pages in this test. I have added theme twenty fourteen, and customized that with styles and styles twenty fourteen, and it all looked good. Then I upgraded to WP 4.0 and the styles function dissapear,a nd I got a msgs saying that I should add the Style fourteen plug, even if it was there. I deactivted all the plugins in network admin, and activated them one by one to se if there was one who ruined it, but no particulare plugin ruined it, I just had to deactivate and activate again,a nd it was all in order. The same happened again, and I was advised to make a child theme to avoid starting all over again. I so did, with the plugin “one click child theme”. It looks good so far, and I got a child theme customized like the original one (after my changes). But after some mins I refreshed the page and suddenly I lost the styles fourteen functions,even if the plugin is active. I have done the whole deactivating/acivate prosecc again, but still style foruteen functions wont show up. What have I done wrong?

Jsu for the record. I have another page where I use twenty fourteen. Its a new page, whee i have used this theme from the beginning. I dont use child themes,a nd I have stules fourteen there,a nd have customized it. No need to have a deactivate/activate process on that one when I updated WP 4.0. The problems are only on my mulitlinguale site.