I finally got a response from DPS on my certificate renewal application. They said that they never got the range test form that I submitted to their site twice and emailed them twice. I emailed it again. While I was preparing to also FAX it, re-submit it to their website, and mail a physical copy via registered mail (and repeat daily), I got an acknowledgment that they had received it. That was late last week.
I have not received anything further from DPS, so, as of today, my instructor certificate has expired, and I will not be permitted to hold any more CHL classes unless and until my instructor certificate renewal goes through. I expect that it will eventually go through, but I have no idea how long that will take.