Amazfit Watch faces

I modified a watchface. Everything seems to be OK and rendered as I expected on my Mi Band 5.
But, the preview image of my watchface shows a black blank preview in the "Band display" option.
Can somebody help me to identify the reason of this issue?

Link of watchface: /mi-band-5/view/815 ...

I modified a watchface. Everything seems to be OK and rendered as I expected on my Mi Band 5.
But, the preview image of my watchface shows a black blank preview in the "Band display" option.
Can somebody help me to identify the reason of this issue?

Link of watchface: /mi-band-5/view/815