You're definitely doing all the right things; it's hard if your players don't cooperate. Let's see.
The first thing I'd try is starting sessions in media res. You can sort of force a bit of momentum if the night starts with the characters under fire in the middle of a combat, or pleading for their lives in front of a judge, or what have you. At the very least the players ought to be curious as to what happened. This may feel like railroading again, however.
Apocalypse World has a nice trick that's sort of like that. For each player, you come up with a list of complications, and then at the beginning of the session you have them roll 2d6. On a 2-6, they choose three complications; on a 7-9, they have to pick two; on a 10-12, they just pick one. E.g., if you were playing a superhero game:
- Your nemesis just escaped from prison
- Your sidekick is downtown; the police caught him robbing a convenience store
- You just found a note claiming to be from your future self; he knows things about you; he tells you that you must throw your next fight with the Living Flame
- You have a patch of scales on your back; nobody else knows yet
Putting the player's fate in the hands of dice reduces the railroading feel. The complications ought to be more tailored to the character, and perhaps more or less serious depending on the feel of your game. They should definitely reflect or be related to ongoing plot, because they need to bring the players' mind back into the game. If doing this for each player seems like too much -- and it might be, if you need to do something to remind them of what's going on each session -- do it with one player per session.
You could also end every session by asking the players to write down their goals for the next session. Save the index cards, and pass them out again when the next session happens, as reminders.
And in general, you probably want to be thinking about ways to make the players more invested in the plot. If they hate the villains, in the good way where they want to see more of them so they can defeat them, that's a good thing.