Your post enabled me to find my solution with not being able to see the Follow button, thank you!
 
 
1 - Try incognito browser window if you have enabled permissions as shown in this article screenshot. We tried clearing cache/history and things like that but got mixed results. Starting a new browser session seems to have helped.
2 - The Permission Settings on the Follow Entity were set to Private. I changed it to Collaborate   
 
 
 
I did not have to make any changes to Post Configuration as it was already active for Knowledge Article (the entity I'm using). Hope this can help others.
Rhonda