Edit button on the top right menu disappeared, how can I get it back? Put my website in development mode in the past but I'm having a hard time finding the setting to re-enable the in field editing of nodes. 

Which configuration setting is responsible for toggling the edit button in the top right corner and the pencil icon on blocks and content?

Edit:

I found out there are many javascript errors, check the screenshot here.
The issue was caused because of an unclosed div tag in multiple blocks on my site. If you have this issue check all related twig templates, blocks and content for unclosed HTML tags.