I just wanted to say to the OP, you are not being properly taught in your church. God disappears for all of us, from time to time. St. John of the Cross calls it "the dark night of the soul." Even Job did not hear from God till his book was almost finished! Chapter 38, if I remember correctly.
I also dislike the advice people are giving you. A relationship with God, including prayer snd fasting, is never a magic spell to use to get what you want. God has a time and a season for everything. He's not a tame lion. (See Narnia stories!)
Instead he is the sovereign Lord of all creation. He rules and reigns. He does not jump when we demand it. I think God is more interested in seeing you grow, than trying tricks so he will save your husband. Read "Knowing God" by JI Packer. He explains in who God is. It's a lesson we all need to learn.
Finally, God may save your husband, if that is his will, but that means being consistent in prayer, no matter how long it takes. I witnessed and prayed for my family to be saved for decades. Finally, my father was dying of Congestive Heart Failure, at the age of 83. My husband and I explained the gospel, and he prayed to accept Christ. God saved him, after 31 years of prayer. The next 5 months, I read the Bible to him, and prayed with him. We listened to Christian music. When I wasn't visiting, he witnessed to the nursing staff, doctors and other patients. It was so exciting to watch him figure it out, without telling him.
Meanwhile, my dad witnessed to my younger sister. She was really mad at me for "taking advantage of him" when he was dying! I was over joyed he was saved before he died. I kept praying for that my sister, but she was a stubborn liberal, very self sufficient. I asked God many times if I should continue to pray for her! Her heart was so hard!
God didn't really answer, so I kept praying. Then, after 38 years of praying for her, she phoned me to tell me about the wonderful Baptist church she was attending. Say what!!? A neighbour had been witnessing, and took her to the church. She said she realized God was real, and Jesus was her Saviour! I was astounded! I was ready to give up, but God was ready to act.
So, please don't give up! And don't put God in a box. He is not beholden to anyone to answer prayer. But, he will answer in his timing and will. Especially when the prayer is for someone's salvation. I have a friend who got saved through the witness of a friend at ESL classes nearly 20 years ago. She has been praying for her husband to be saved, ever since. Many of us have talked to him, shared our testimonies and the gospel! My husband and another strong Christian man did too. I personally asked him what was holding him back from knowing Christ. He had no answer. But his wife, my friend, has not given up and they have a great marriage. I have no doubt God will save him.
And God is very real, and he loves you! Don't ever give up when you are discouraged.