Obama tried and the Castros screwed him for it. Spent the whole time whining about Guantanamo. Then Democrats lost Florida in the next election

Then they had to go and support the war against Ukraine. If those issues were not enough, i'm not convinced the regime there even wants the embargo lifted since it gives a convenient scapegoat for their own economic incompetence. Not saying the embargo is right but politically nobody is going to try again for a long time. There is little to be gained on the US side and a lot to lose due to the large anti-Cuba vote in a large swing state. It is what it is.