[Closed] No more language option on article

Background of the issue:
I'm trying to fix a WPML bug after updating by manually adding a link 'En' to all of our articles, but I can't find the language tab on my articles. More details can be found here: https://wpml.org/forums/topic/no-more-language-selector-after-upgrading-wpml-on-posts-only/

Symptoms:
The language tab is missing on my articles, preventing me from applying the fix.

Questions:
Why is the language tab missing on my articles?
How can I manually add the 'En' link to my articles without the language tab?