Did you installed your dependencies on your remote server? If yes, try installing your app as a module.

Given a the following directory structure:

/yourapplication
/yourApplicationMainFolder
    __init__.py
    /static
        style.css
    /templates
        layout.html
        index.html
        login.html
        ...

Create a setup.py file on /yourapplication/setup.py with:

from setuptools import setup

setup(
    name='yourApplicationMainFolder',
    packages=['yourApplicationMainFolder'],
    include_package_data=True,
    install_requires=[
        'flask',
],)

Install with pip:

pip install -e .

If that did not work, comment out all your imports in the main script and inspect one by one to see which one is the problem.

I have solved it, reinstall all libraries again.

To future readers: something that might not be obvious is you can get more details on the import error by doing the following:

• Remove all import lines from your __init__.py file
• Run flask and navigate to the page it is hosted on
• While flask is running re-add the import lines to your __init__.py file and let flask update at run time
• Refresh the page in your browser.

You should now get more detailed information in the browser as to which line is causing the import error along with a traceback.

In my case, there was an error in importing a specific library on FLASK_APP file. Running the command python app.py as jluu suggested will help you to know exactly when the ImportError happens.