[Cerrado] ATE translations not available on site copy

Background of the issue:
I made a copy of the site enlace oculto as we are currently renewing the theme. Upon installing the staging site, the migration tool dialog prompted on the screen, and I set it up as a copy, with the original site still running.

Symptoms:
ATE translations were not synced. Instead, the original language was shown on some strings, all flagged in orange as 'flagged for later', and some strings were simply blank. Attempts to connect sites using the translation tools and to delete the site copy key and create a new development one were unsuccessful. Troubleshooting clean-ups yielded identical results.

Questions:
Why are ATE translations not synced on the site copy?
How can I resolve the issue of original language showing instead of translations?