Problem #1: It can't pass without eliminating the filibuster. Even though the Democrats have said they want to eliminate it the next time they're in power, Republicans don't want to be the first to take that step.

Problem #2: Some Republicans aren't really making it a priority.

If Republicans are going to nuke the filibuster, there's a whole bunch of wishlist items they could ram through. Unless they're going to do something extreme like repealing the Civil Rights Act, Voting Rights Act, or gun control laws, it isn't worth nuking the filibuster.