Jekyll tag pages only build locally but not with GitHub Pages

Hi all,

I have a Jekyll blog. Each post has a tag that links to a “tag page” with a list of all the posts with the same tag.

It’s built locally but when I serve it up with GitHub pages, it links to the 404 page.

I thought it’s a timing issue(give GitHub pages some time and it will go away, which happens most of the time) but it doesn’t seem like it. 

Can you give me some directions? Thanks in advance.

Here’s the repo: https://github.com/ming-yong/ming-yong.github.io

Here’s the website: https://ming-yong.github.io/

Expected:

Reality:

The case sensitive link is working fine for me: https://ming-yong.github.io/tags/Year%20in%20Review/

I see! My files have names in uppercase. Thanks for spotting that, @chrisk91 !