Hey there, I’ve run into this exact error plenty of times—let’s break down the fixes that actually work, since slicing the image alone won’t resolve the core issue with Smart Objects.

Why this error pops up #

Smart Objects act like embedded containers for external files (or other Photoshop layers), so you can’t edit their pixels directly without first accessing or converting the layer. Here are the most reliable solutions:

• Rasterize the Smart Object (quick, one-time fix)
  Right-click the Smart Object layer in your Layers panel, then select Rasterize Layer. This converts the Smart Object into a regular pixel layer, letting you edit it freely. Note: This is irreversible—you’ll lose the ability to edit the original source file later, so duplicate the layer first if you might need to tweak it down the line.

• Edit the Smart Object’s source file (preserves non-destructive flexibility)
  If you want to keep the Smart Object’s reusable properties, right-click the layer and choose Edit Contents. Photoshop will open the original source file (usually a PSD, but could be PNG/AI too). Make your edits there, save the file, then switch back to your main document—your changes will automatically update in the Smart Object.

• Replace the Smart Object (if source is missing/corrupted)
  If the original source file is lost or damaged, right-click the Smart Object and select Replace Contents. Navigate to the correct source file on your computer, select it, and Photoshop will refresh the Smart Object with the new content, restoring editability.

• Check for nested Smart Objects
  Sometimes Smart Objects are nested inside other Smart Objects. Double-click the outermost Smart Object to open it in a new window, then check if there’s another Smart Object inside. Repeat the steps above (rasterize or edit contents) on the nested layer, save, and return to your main document.

If you tried slicing before, that operation was likely targeting the locked Smart Object layer—fixing the Smart Object itself first will let you perform any edits you need, including slicing.

内容的提问来源于stack exchange，提问作者Dil Shah Dirar