This photo was uploaded 5 days ago and it shows perfectly good.
I rebuild Discourse but this problem remains. Hope someone find the reason and solve this problem.
oops, this problem is caused by hostname. A month ago I used “qinyujie.xyz” as my hostname, but I abandon that hostname later because in China we should put on records in the public security bureau and that needs a lot of time.
thanks Sam. Using discourse remap I soloved this problem.