Facebook doesn’t automatically show you notifications when a post is made by a friend or on a Page you like. You have to take action to see them. It’s a simple procedure, though:
Visit the Page you want to receive notifications from
Hover over the like button, and click on it. You must like a Page or person to get their notifications. 
Continue hovering. A drop-down menu will pop up. Click on “Get Notifications”. 
When the checkmark appears next to “Get Notifications”, you’ll receive that person’s – or Page’s – notifications. 
This also works when you mouseover the name of a person or Page in a comment
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