Does anyone here have experience with Cydia repository development?

I got to develop this for someone on fiverr, but he keeps getting a "404 packages not found" and "some index files cannot be downloaded" error when trying to install the repository in Cydia.

I don't have a jailbroken iPhone device, so I was limited to troubleshooting on my browser environment, and I know the URL is very much correct, and the Packages file exists but it still doesn't work in Cydia.


What else can be the issue since the Packages file exists?