“do not pray for this people.” God had said this to Jeremiah earlier (Jer. 7:16), He says it here in Jeremiah 11:14, and He will say it again (Jer. 14:11).
[For more on Jeremiah not praying for the people, see commentary on Jer. 7:16. For information on God not answering the prayer of the wicked, see commentary on Amos 5:22.]
“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 come.