@Swoop1990 Getting this too. I have found that if you play around with it you can get success, but it’s very annoying.
Like when you select the player you want to substitute, you have to select A (Xbox), and before it pulls up the names of available players to sub, you hit A again. Has to before the subs populate. This will sometimes highlight the players like it should and you can sub as normal. If that doesn’t work, just press LB to cycle offense and defense and refresh the screens and try again. However, this doesn’t work every time, but I actually did sub 2 players successfully last night after playing around with it for a while. Please have this looked at EA. Formation subs don’t highlight players when you are trying to sub and it works intermittently, but we are doing it blind and guessing which player we are subbing is highlighted. Very hard to do this.