Disabled toggle switch

Hi Everyone,

After setting up Slack and the Notification Preferences, the Slack column does not have switch buttons (for both online or offline) to toggle notifications on and off. It only says "Disabled" instead. Here's a screenshot:
https://drive.google.com/file/d/1-I91dUdgs320LXNfxdbua1YKkLI2JDl1/view?usp=sharing

Does anyone know how to fix this? 

Thank you.
Catalino
