ineffective
adjective uk/ˌɪn.ɪˈfek.tɪv/ us/ˌɪn.ɪˈfek.tɪv/
不起作用的，无效果的，不奏效的
not producing the effects or results that are wanted
They made an ineffective attempt to get the rules changed. 他们试图改变规则，但未成功。
The army has proved ineffective in protecting the civilian population. 军队没有起到保护平民的作用。