updated 06/22/2018
Problem solved as it seem to because of i didn’t check the box in attachment display setting”link to media file”, the last post was also fixed.
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It figured out that the Lightbox plugin was not working when i posted the article yesterday.
Today i made a change for a more recently updated plugin called Simple Lightbox ,no difference at all .Then i deactivated all plugin and replaced the theme for the official one .Nothing happened.
The latest time when i remember it working was months before ,after i posted the article in Shanghai.After then i almost made no change,except for normal plugin & wordpress update.It’s hard to fix it for me as i merely know nothing about php language…