Check whether the file is actually transparent
Open the PNG in an editor or slide tool and place a colored rectangle behind it. If the color shows around the subject, the file contains transparency. If a white rectangle stays visible, the white pixels are already part of the image.
Use the saved file for this test rather than a screenshot or thumbnail. A file browser may show every image on white even when the PNG itself is transparent.
The clipboard can change what reaches the next app
When you copy an image, the source app decides what image data to place on the clipboard. The destination then decides which version it can read. Some combinations keep the alpha channel. Others paste a flattened preview with a white or black background.
That is why the same PNG can work when inserted from a file but fail when pasted. The transparent file is fine; the problem appears during the handoff between the two apps.
A screenshot will not solve this problem. It captures the page as a finished rectangle and usually turns the transparent area into whatever color was visible behind it.
Use the saved PNG when pasting fails
First try pasting into another app that supports transparent images. If that works, the original destination is the limiting step. If you need to use that destination, download the PNG and use its Insert image or Upload command instead of the clipboard.
Avoid saving the result as JPEG while troubleshooting. JPEG always needs a real background color, so it cannot tell you whether the transparency survived.
Check the output setting before copying with ClickCutout
In ClickCutout, choose PNG or WebP for a transparent copy. The JPEG setting adds the selected background color to copied images too. If you left JPEG selected for a previous product photo, switch the setting before copying your next cutout.
Once PNG or WebP is selected, compare Copy with a downloaded PNG inserted in the destination. If only the pasted version has a white background, use the file insertion route. If both show a white box, inspect the downloaded file over a colored shape before making another cutout.
