Method Not Allowed The method is not allowed for the requested URL

I run the code successfully at my own mac, but when I deploy it to my server, it shows method not allowed after I submit the form.

my website is shiqiu.pw

I don't know why.

I have checked the code deployed on my server is the same as which run at localhost on my mac.

code is here:github (format problem at stackoverflow, so I upload code to github)