-404 when I launch some repositories

Hi All,
I created a github account for one of my students. I created the html code in sublime text from her laptop. It works perfectly when we do view in browser in the laptop. Then I uploaded it to github using the github desktop. It gets uploaded and I can see the index.html & README file I initialized the repo with. When I launch using github pages, I get a -404 https://incognitolavender.github.io/HTML/. This is from a mac book. The user for the macbook is 12 year old.
I did the same with another student of mine, who is 11. His is windows, he runs into the same problem.
I used both their accounts, created a new repo from my laptop, uploaded the index.html with my laptop. I upload it to github online repo. When I publish, it works,

So the issue seems to be laptop dependent. I am not sure what to check. Has someone faced this problem?

Hey @Padmaramani and welcome! For https://github.com/IncognitoLavender/HTML the issue seems to be that the Index.html filename is capitalized. This makes it not visible on the / route, but I can see the file if I explicitly visit /Index.html. Fix it by renaming the file.

As a side note, usually if you see a difference on two different machines on the same page/site, try clearing the cache or visiting the page/site in your browers’ Incognito mode.