Helicon Remote 3.9.11, Samsung Galaxy Tab S3, Android 9, Nikon D850

Everything used to work just fine, but it's been over a year since I've taken any stacks. When I went to take some today, I was unable to. This is what happened:

1. Turn off camera. Assure Helicon Remote currently not running on ...

I'm trying to record video with my Nikon D850, using Helicon Remote, but it's behaving badly.

Setup: D850: Live view set to movie and on. Tethered to Samsung Galaxy Tab S3 (Android tablet).

In the app, I've verified that Live View is on and I can see what the camera's seeing (the image changes as ...