I'm sorry I wasn't able to get my point across.
This is like going to Walmart and buying a lawnmower (OpenGarage) that comes in a box (Blynk). I can't get the box open. It has nothing to do with the lawnmower.
The Blynk app's QR scan page wouldn't scan the code on the paper that came with the OpenGarage hardware. However, there is an image of the code on the opengarage.io website, and it did scan that. This revealed to me that, unlike most QR scanners, there IS no reticle or guide to positioning the code in the image; there IS no vibration or beep when a code is accepted; and there apparently IS no error message if the code is read but rejected -- which is what I think was happening, as there's been a firmware update since the printing of the paper.
Although I have over 40 years experience in IT, none of it is in Linux or the IoT. I find that the vast majority of documentation for these are based on these principles:
1. Assume the reader knows what you're talking about, and so doesn't really need TFM;
2. Proceed logically from there.
Opengarage starts blithely talking about widgets as if the newbie knows what the hell those are. The same thing happens in this thread. All I want to do is open my friggin' garage door.
My latest problem is that Blynk doesn't show up as a search result in the AppStore on my iPad. Nor is there any information from OpenGarage about how to use their Blynk app, now that I have it on my Android phone. I've pushed everything and nothing happens. Alas, these are problems for other posts. Thanks to those who tried to direct me here.