“do not pray for this people.” God had said this to Jeremiah earlier, and He will say it again (Jer. 7:16; 14:11; see commentary on Jer. 7:16).
“I will not listen to them.” God tries and tries to get people to listen to Him and obey him. But those who consistently ignore and defy God will suffer for it, and when their suffering comes, very often they will call out to God and He will not hear them (cp. Prov. 1:22-28, esp. v. 28).
“trouble.” The Hebrew is more literally “evil,” that is, when evil times come; when trouble and disaster comes.