try

Dockerfile

@@ -8,4 +8,4 @@ RUN pip install --no-cache-dir --upgrade -r /code/requirements.txt
 
 COPY . .
 
-CMD ["gunicorn","-b", "0.0.0.0:7860", "main:app"]
+CMD ["gunicorn","-b", "0.0.0.0:7860", "main:app"]

main.py

@@ -58,7 +58,7 @@ def callback():
 
     return 'OK'
 
-@handler.add(MessageEvent, message=TextMessageContent)
+@handler.add(MessageEvent, message=(TextMessage, TextMessageContent))
 def handle_message(event):
     with ApiClient(configuration) as api_client:
         line_bot_api = MessagingApi(api_client)