Problem: WPML in multisite does not show up in the admin menu of the main website.
Solution: Search for "_wpml_inactive" within your database. Once you find it update manually from 1 to 0 and save. The menu will then show up in your wp-admin.
You can find the "_wpml_inactive" with this query (changing wp_ to your prefix):
SELECT * FROM `wp_options` WHERE option_name = '_wpml_inactive'
Problem Description: Different domain per language WPML's option doesn't work.
Solution: Check that your domains are pointing to the correct environment. For this disable WPML, now you should display the same content in both domains? (Without any redirection).