This thread is resolved. Here is a description of the problem and solution.
Problem: I can't see all language pairs available in WPML > Translations
Solution: you need to set language pairs for the user in order to see translations in a certain pair, even if the user is a translation manager
Relevant Documentation: https://wpml.org/documentation/translating-your-contents/working-with-translation-managers/
This is the technical support forum for WPML - the multilingual WordPress plugin.