Sometimes, no matter how much we wish for it not to happen, our muses won't cooperate. We know we need a good idea to move our works-in-progress forward, but we seem to have written ourselves into a corner.
That's when I break out the anti-muse. I go back a chapter or so in my story and change the POV character reaction to the complete opposite of what I' d previously written. (There's a part of me that wants to tie things up neatly, but if I do that too soon I have no story.) Changing the outcome of an event or a reaction puts a new spin on things. It changes the situation, making it full of conflict, making my muse happy.
Another nudge for a wayward muse is to give the POV character(s) exactly what they want. The journey that I'd intended them to take for the whole book gets resolved right then in the story, BUT reaching their goal has to make things go from bad to worse. Consequently, a new goal forms, with a fresh set of obstacles in it's path.
On days when the words are there but they seem insipid or uninspired, I take a different approach. I create something visual with my hands, using art and craft supplies. Sometimes the object created is a tip from the subconscious, sometimes its a gateway to new ideas. Allowing my brain to work creatively from a different thought center always jumpstarts an unresponsive muse.
I can't speak for all writers, only myself. These cures came from the school of hard knocks, honed through years of trying to understand how I write. Perhaps you have a few of your own to share?