You can't delete a file attached to a comment from the Attachments panel; Delete File will be grayed out.
To delete a file attached to a comment you must delete it from the comment itself, or delete the comment that the file is attached to.
To go to the comment from the Attachments panel, click comment under the filename.
Delete a file attachment from the comment panel
- Click the More icon to the right of the comment.
- Select Edit comment.
If Edit comment is grayed out, it's likely that you don't have the correct permissions to delete the attachment. Contact the person who left the comment and ask them to delete the attachment, or contact the Owner or an Admin on the sheet to request they delete the comment.
- Hover over the attachment you'd like to delete and click the Delete icon.
The file should now be removed from the comment and the sheet.