God always answers our prayers, but not always right away or in just the way we expect Him to. Sometimes He says "yes", sometimes He says "no", and sometimes He says "wait".
When we pray for others, there are a number of factors which affect the whole process, including you and your condition, God and His Will, and the condition of those for whom you are praying. you don't control the outcome of your own prayers completely, others don't control it completely, and God has specifically limited Himself not to control it completely, which, of course, is one reason why you don't always get the answer right away. The trouble may be with you, or it may not be God's time to act or move, or the trouble may be at the other end, with those for whom you are praying. But when the conditions are ready for the result God knows is best, He will answer.
When the Lord doesn't answer us right away, it tests our faith and draws us closer to Him, but His delays are not denials! (Jam.1:3) So never doubt for a moment that God is going to answer--and He will! He has to! Trust Him! And thank Him for the answer--even if you don't see it immediately!