MERN app works locally but not on Railway

I was able to find out that this is a 400 type error. I tried restarting the deploy, changing the default port and checking the link to the site. I also cleared out my caches. I would’ve thought that it was size of the file, but this site was working before. I needed to redesign it though and that’s when things started going wrong

When I checked the Build Logs it said the following

#11 0.770 npm
WARN config production Use `--omit=dev` instead.

But I’m not sure where to add the omit=dev line.

Additionally, I tried deploying the app to heroku but it kept saying “Not Found” there too.

The deploy logs didn’t return any errors. It just says which server the app is running on. Please help. I’ve been trying to fix this error for months.

If it helps, my repository is below