When using Meteor 1.5, index.html doesn't respond to changes

I’m trying to set up React with the newest version of Meteor, but my HTML page is unresponsive to changes. Nothing I add to the index.html file in the client is shown when the app is run, leading to React error Uncaught Error: _registerComponent(...): Target container is not a DOM element..

Literally, nothing I do to the index.html page is registered by Meteor.

I deleted the Meteor directory, created a new one and everything works fine now.

Probably one of the packages I installed corrupted it. I’m thinking Meteor Toys, but who knows.