also: なっていない
expression
unacceptable; no good; inadequate
Colloquial negative of なる, used to say something is not up to standard, not working, or a complete failure. Often used in casual speech to criticize a situation, performance, or result.
この計画はなってないよ。
This plan is no good.
彼のやり方はなってない。
His way of doing things is unacceptable.
そんな言い訳はなってない。
That excuse is completely inadequate.
ならない is the standard negative of なる, used in formal or neutral contexts, whereas なってない is a colloquial contraction used mainly in spoken Japanese.
Contraction of なっていない, the negative te-iru form of なる (to become). The phrase literally means 'has not become', and by extension 'is not in an acceptable state'.