await bot.process_commands(message)

app.py

@@ -115,6 +115,8 @@ async def on_message(message):
             # post to slack only if thread already exists
             post_to_slack_forum_version(message, SLACK_CHANNEL_ID, message.content, message.author, thread_ts=slack_thread_ts)
 
+    await bot.process_commands(message)
+
 
 @bot.event
 async def on_thread_create(thread):