I got a response on Discord from @lah7, who told me basically that he used to be able to sync the translations, but he no longer has a Transifex account to do so. I just created myself a Transifex account, and asked @Wimpy (who appears to be the only one left who can sync the Ubuntu MATE Transifex) to either sync the new translations himself or give me syncing capability for the Ubuntu MATE projects.
Obviously I'm witing for a response to that, but whichever one he chooses, I have faith that your translations will get synchronized and applied to the working start.ubuntu-mate.org Web site. I shall keep abreast on this topic as the situation unfolds, and on behalf of everybody else here, I appreciate your contribution of translations. Thank you.