There are actually many types of writers block. (this is from an article by Charlie Jane Anders.)
This is very common for many writers. You have a perfect story and it's going great and then... flop. You just get stuck right in the middle. The best advice I have ever come across for this situation comes from Roald Dahl "Always stop at the most exciting part in your story so then you always have something to come back to." However tempting it may be to write more at that exciting moment DON'T. It will still be there when you come back. If you are afraid you will forget what happens write yourself a little note to remind you. You don't want to waste all of your energy on that one part and then burn out.
3. You have a terrible feeling your story took a wrong turn a hundred pages back, and you only just hit a dead end.
This one just plain sucks. You made a decision and then it ended up sucking. It's solution isn't very comforting either. In this case you could turn your story back around and keep going pretending that it was the plan all along. Or if that isn't possible, you could partially rewind going back only fifty or so pages instead of the entire hundred.
4.You're bored with all these characters, they won't do anything.
You have created these amazing characters and you've written several pages about... Them eating and feeding their cats. Fortunately these pages can actually help you. Maybe a conflict comes up and viola! You suddenly have a plot, or someone is looking like the protagonist. Don't be afraid to meander a little bit and experiment.
5.You had this incredibly cool story in your head, and now you're turning it into words on a screen and it's suddenly dumb.
It's possible you're actually seeing a real problem with your idea, and with the execution. And, you know, there's nothing wrong with abandoning a novel and starting afresh. Sometimes these dead half-finished novels serve as great fertilizer for the awesome novel you're going to end up writing.
But don't give up too fast. It's possible that part of your idea is salvageable, or that the idea is genuinely cool and you've gotten yourself stuck into a weak execution of it. Sometimes it's helpful to step back and write a synopsis of the stuff you've already written, so you can see how it fits together and whether there are some buried parts that should be turning points in the story.
Constant Vigilance! Hope this helped.