Hi Mike,
If the flash triggers when you press the shutter to take a photo then it's most likely to do with the camera exposure settings and flash mode setting.
My flash settings (for macro) are 1/16, 24mm, M mode, and I can get a good "test" shot from the the flash by pressing the red button. The batteries are "fresh". The flash is not in "Slave" mode.
My R10, as far as I can see in the menu, has external flash "Enabled" .
I shoot in (M) manual mode, manual focus, auto ISO.
The two parts I made bold are the important parts, but I will address them in reverse order.
EOS R10 works differently with auto ISO depending on the lens used. With an RF or RF-S lens the ISO can range from ISO 100 to ISO 6400. With a lens on the mount adapter the ISO range is ISO 100 to ISO 1600.
You are using manual exposure on the camera, what shutter speed and aperture values do you use?
So to the flash, you have chosen manual flash exposure at 1/16th power with the flash zoomed to 24mm. This could be the cause of the problem. If your camera settings for aperture are say f/8, f/11 or more then you may not get enough light from the flash to correctly expose the subject resulting in a black frame. Also the further away the subject is the more power you need. You mention macro, I wonder how close as the flash might not be able to illuminate the subject really close to the camera as the light from the flash actually passes above the subject.
I have some thoughts…
If you are photographing macro subjects you need to decide if the ambient / daylight is important or not in the frame.
Ambient light not important - black background is ok
If the ambient light is not important then set the camera in manual mode to 1/250th, with ISO 100, then choose the aperture you need for the depth of field. Then set the flash to ETTL so that the camera can control the power level for you. The result is that the ambient light is very underexposed and the flash lights the subject.
Ambient light important - balance of flash and ambient needed
If the ambient is important, then you can still use manual exposure, but you need to use a shutter speed and ISO that will give the correct exposure for the daylight. I still prefer to set the ISO manually but you can use ISO auto. Then set a shutter speed so that the ambient light is looking as you want. Then set the flash to ETTL so that the camera can control the power level for you.
Hope that helps,
Brian
