React-Redux - No reducer provided for key "coins"

Ah just found it, I was importing my coins reducer incorrectly...

import { combineReducers } from 'redux'
import coins from './coins' // because I have coins/index.js

export default combineReducers({
    coins
});

instead of

import { coins } from './coins'

Your issue lies with how you're importing your coins reducer:

import { coins } from './coins'

The latter tries to obtain a named export returned from the file in ./coins.

You are not using any named exports only export default, therefore you just need to import the file as follows:

import coins from './coins';

Using the latter will result with the fact that coins will then contain the value of export default; which will be the coins reducer.

Even when all your imports are correctly imported, this can still happen for one other reason. Circular Dependency!

In my case, this happeded because of a circular dependency in a file. I had two circular dependecy in the project that I created accedentally. Example: rootReducer.ts -> authSlice.ts -> rootReducer.ts.

These dependencies are often not as easy to debug. I used this package to check for circular dependencies. Once the circular dependency was removed, all was well.