PROBLEM Upgrade Check Failed

[kasztelan]

I checked my website today and saw that there was 3.3.13 version of Gestsimple and saw that Upgrade Check Failed. And link to download.
So I did with the last version and now I have somethink like this:

GetSimple Version          3.3.15          Upgrade Check Failed !          Download

How can I solve this? Till now everything was OK. Always I was able to upgrade through the website.