Python Flask: TemplateNotFoundが消えない

実行環境

Python 3.7.0
PyCharm Professional 2019.2 version
Jinja2==3.0.1
Flask==2.0.1

実現したい事

Python Flaskの勉強中なのですが，以下のコードをもちいてlocalhostでindex.htmlの内容を表示したいと考えております。

試したコード

python
1from flask import Flask, render_template
2app = Flask(__name__)
3
4@app.route("/")
5def index():
6    return render_template('index.html')
7
8if __name__ == "__main__":
9    app.run(debug=True)

html
1<!DOCTYPE html>
2<html lang="en">
3<head>
4    <meta charset="UTF-8">
5    <title>Title</title>
6</head>
7<body>
8<h1>Hello world</h1>
9</body>
10</html>

フォルダ構造
flask-aap
|- app.py
|- templates
|-- index.html

Errorの内容

ブラウザ上に，以下のErrorが表示され，index.htmlが表示されません。

jinja2.exceptions.TemplateNotFound
jinja2.exceptions.TemplateNotFound: index.html

Traceback (most recent call last)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 2309, in call
return self.wsgi_app(environ, start_response)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 2295, in wsgi_app
response = self.handle_exception(e)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask_cors\extension.py", line 161, in wrapped_function
return cors_after_request(app.make_response(f(*args, **kwargs)))
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 1741, in handle_exception
reraise(exc_type, exc_value, tb)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask_compat.py", line 35, in reraise
raise value
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 2292, in wsgi_app
response = self.full_dispatch_request()
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 1815, in full_dispatch_request
rv = self.handle_user_exception(e)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask_cors\extension.py", line 161, in wrapped_function
return cors_after_request(app.make_response(f(*args, **kwargs)))
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 1718, in handle_user_exception
reraise(exc_type, exc_value, tb)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask_compat.py", line 35, in reraise
raise value
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 1813, in full_dispatch_request
rv = self.dispatch_request()
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\app.py", line 1799, in dispatch_request
return self.view_functionsrule.endpoint
File "C:\Users\nakajyu1\drml\backend\main.py", line 24, in index
return render_template("index.html")
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\templating.py", line 134, in render_template
return _render(ctx.app.jinja_env.get_or_select_template(template_name_or_list),
File "C:\ProgramData\Anaconda3\lib\site-packages\jinja2\environment.py", line 869, in get_or_select_template
return self.get_template(template_name_or_list, parent, globals)
File "C:\ProgramData\Anaconda3\lib\site-packages\jinja2\environment.py", line 830, in get_template
return self._load_template(name, self.make_globals(globals))
File "C:\ProgramData\Anaconda3\lib\site-packages\jinja2\environment.py", line 804, in _load_template
template = self.loader.load(self, name, globals)
File "C:\ProgramData\Anaconda3\lib\site-packages\jinja2\loaders.py", line 113, in load
source, filename, uptodate = self.get_source(environment, name)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\templating.py", line 58, in get_source
return self._get_source_fast(environment, template)
File "C:\ProgramData\Anaconda3\lib\site-packages\flask\templating.py", line 86, in _get_source_fast
raise TemplateNotFound(template)
jinja2.exceptions.TemplateNotFound: index.html

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