Katie M. Stout just posted eloquently about "hitting the wall," and it has become such a familiar story that I think it may just be a phase in many (most?) writers' lives. Which is not to say it's easy, or trivial. It can last a season, or years, or anything in between. It can be brutal while it lasts. I've gone through my own version of it.
what I've seen happen to so many writers is that the well refills, one
way or another. As Katie Stout says, the writers' goals often change.
What the writer writes, or for whom, or how, can change. There is a door
in the wall--invisible as it may be for a while--with new territory on
the other side.