If GIMP's Eraser leaves a solid black or white patch, check whether the active image layer has an alpha channel. A layer without transparency cannot expose a transparent hole through ordinary erasing. Also confirm that you are editing image pixels rather than a mask. Increasing eraser strength or asking an AI editor to regenerate the background does not resolve those document states.
Identify the layer that receives the stroke
Keep the original file and work on a duplicate. Select the intended image layer in the Layers dialog, checking its thumbnail and whether a mask is attached. The appearance of the whole composition cannot tell you which drawable is active. A lower white layer can remain visible through a successful erasure, so a white patch alone is insufficient evidence of failure.
Read the layer's alpha state using the current GIMP interface. Use Layer > Transparency > Add Alpha Channel when that image layer lacks it; an unavailable command can mean alpha already exists. Do not conclude that an unavailable command always indicates a broken installation. Confirm the selected layer first.
Run a small transparency comparison
This is a reproducible test plan, not a completed test. Put a brightly colored temporary layer underneath the photograph. On the working image layer, erase a small area away from the subject. Record whether the result shows the toolbox background color, the temporary lower layer, or no visible change.
Undo the stroke. If the image layer lacks alpha, add an alpha channel and repeat the same stroke with the same tool settings. Seeing the temporary layer through the hole provides stronger evidence than relying on the checkerboard alone. If nothing changes, investigate selection boundaries, layer locks, opacity and the active target instead of adding alpha repeatedly.
Separate transparency from mask editing
An image layer and a layer mask serve different purposes. A mask controls visibility using grayscale values. Painting or erasing on that mask changes which parts of the image appear; it is not the same operation as changing the photo's color channels. Choose the image thumbnail when you intend to erase pixels, or deliberately edit the mask when you need a reversible visibility change.
For a product cutout, a reversible mask may be more convenient than destructive erasing. Preserve the original layer so that a mistaken edge can be corrected without recreating the product's shape. Neither approach makes a drawn checkerboard into genuine transparency.
Check the delivered file
Save an editable master and export a separate copy in a format that supports transparency. Reopen the exported file over a contrasting background. The acceptance condition is a real opening in the intended area, intact product edges, and no unexpected solid black or white pixels.
GIMP commands described here belong to the external editor. An Imagild Photo Editor result can be inspected in this workflow, but this guide does not promise that Imagild exposes GIMP's alpha controls. Fix a correct image's document state before spending effort on a new creative generation.