Hey @kazooi, I know you have resolved the issue, but If you want I can share some insight on why they happened.
1 - Casing of the import, and why it matters.
Some OS are case insensitive, like Microsoft and MacOS, but Linux on the other hand is case-sensitive.
So on a Windows/Mac looking for a ./navigation folder will work. But when deploying/running your code in a Linux environment won’t work because there’s no such folder with the lower case n.
2 - I did not upload the project with node_modules folder
You are right, you don’t upload them… but that doesn’t mean they are not used.
Vercel (or any other service provider) will build your app and then deploy it.
Building means also building the necessary node_modules, which will end up in the production build, thus in the code shipped to the client.