Suddenly unable to write

Have you ever suddenly been unable to write on your project? Where the ideas are there but words just stop and the ability to formulate coherent sentences vacates your brain?

Everything just comes out like mush and there is nothing to even build on. It gives me the sense of walking into a room and forgetting why I was there.

I’ve been trying to follow all the advice I can find — take a walk, take a break/put it away for a while, work on other projects, read and enjoy other media, troubleshoot the sticking point — and none of it has made a difference. It’s been weeks with no progress and it is so frustrating.