Category Widget

what are the settings for the permalinks?
http://codex.ww.wp.xz.cn/Using_Permalinks

does that also happen if you temporarily switch to the default theme Twenty Fourteen?

what happens if you deactivate all plugins?

have you contacted the developer of your theme for support?

as you seem to be using a commercial theme, it might not be supported here in the forum; http://codex.ww.wp.xz.cn/Forum_Welcome#Commercial_Products