Error: Actions must be plain objects. Use custom middleware for async actions

If you got that error, it's likely that you forgot to import the redux-thunk and configure it accordingly similar to the code below:

import { createStore, Store } from 'redux';

import { reducersRoot } from './reducers-root';

import { IAllState } from './all-state';

export function configureStore(): Store<IAllState>
{
    const devTools: any = (window as any)['__REDUX_DEVTOOLS_EXTENSION__'];

    return createStore(reducersRoot(), devTools && devTools());
}

Solution:

import { applyMiddleware, compose, createStore, Store } from 'redux';

import { reducersRoot } from './reducers-root';

import { IAllState } from './all-state';

import ReduxThunk from 'redux-thunk';

export function configureStore(): Store<IAllState>
{
    const middlewares = applyMiddleware(ReduxThunk);

    const composeEnhancers = (window as any)['__REDUX_DEVTOOLS_EXTENSION_COMPOSE__'] || compose;

    const composed = composeEnhancers(middlewares);

    return createStore(reducersRoot(), composed);
}