He said: {Nay, but he has not accomplished} (80:23), meaning: he has not fulfilled {what He commanded him}, meaning: the disbeliever has not performed what Allah commanded him.
قَالَ: ﴿كلا لما يقْض﴾ أَي: يصنع ﴿مَا أمره﴾ يَعْنِي: الْكَافِرُ لَمْ يَصْنَعْ مَا أمره الله.