Problem about Activating a plugin

Sorry,I can’t view Codex in my computer(Do anyone knows why?)And are confused with the problem.

when I click the “activate” button in options,the plugin doesn’t work at once,But when I log in later it works well.Some plugin(like Recent_comment)are unable to activate now,But it do appears the text “the plugin has been activated”

Do I express the problem clearly？

thanks for you all:)