This thread is resolved. Here is a description of the problem and solution.
Problem: I am trying to translate the translate Woocommerce product Custom Tab Content.
Solution: Edit the original product, add some text for the Tab Title, check the Translation is complete box, and hit Save & Close. Now, the custom tab content is displayed on the translation. This section appears only if you add a title for it.
This is the technical support forum for WPML - the multilingual WordPress plugin.