The first time I took off Sim Rate didn't work at all. I couldn't speed up time, or slow it down. I thought maybe it did not work with this aircraft although that'd be a first...
The second time I took off Sim Rate worked fine. It went up and down and then I left it on 4x as it was a long flight. As I neared my destination it no long worked. I was stuck at 4x and seemingly had no way out of it.