Can't get Apple Lightning/USB camera adapter to work any more! (Last used Sept 2019)

Starting about eight years ago, I've used an Apple USB (Type A) camera adapter to transfer photos from my DLSR camera(s) to my iPad or iPhone without removing the memory card. I've done this with three different Canon cameras and several different iPhones and iPads over the years, so I was very familiar with what had been a simple process:

1 - connect the USB cable to camera

2 - turn the camera on, if it was not already on

3 - connect the USB cable to the USB port of the the adapter

4 - plug in the Lightning cable to the iPad or iPhone

Sometimes I had to turn the camera off and on to trigger the detection of the connected camera, but the Photo Import screen would come up where I could select pics to transfer, optionally deleting them after the transfer, and then to view/edit the photos, share them, etc., from my device.

I hadn't done this since September 2019, the pandemic kind of shut down my photography for a long while. Today, now with a new iPhone 12 Pro (formerly iPhone X) but still the same first gen iPad Pro, I found that using the same adapter, and the same camera, no longer does.. .Anything. At all. No error message, no nothing.

I've tried both my iPad and iPhone, I've used different USB cables, two cameras, even got a second Apple USB A camera adapter, tried reversing the up/down polarity on the Lightning plug head... Nothing ever triggers the import or even acts like anything has been plugged in.

However, if I use these USB cables and connect my cameras to a PC, it detects and imports immediately.

I've always updated iOS to the latest version; has something changed in iOS since Sept 2019 to require some kind of menu enabling for the camera adapter to work now?