I have just noticed that since a certain dive on, the tank pressure line color that previously had different shades of green to red according to pressure gradient, became plain grey.
This is almost always because you haven't filled the tank size details.
The pressure line is colored by SAC rate, and to get the SAC rate we
need to know the tank size. With an unknown tank size we just make it
gray.
And yes, it's a bit silly, because the actual pressure color doesn't
really depend on *absolute* SAC rate, but on relative one, and so it
gets the same color regardless of what the tank size actually is. But
since it's the same code that also calculates the actual SAC rate that
we report textually, the code wants the actual real tank size..
Another reason for a lack of SAC-rate (and a gray line) is if you have
several gas cylinders, and subsurface can't figure out when each
cylinder is used. At that point, subsurface simply doesn't know *when*
you were breathing some cylinder, so it can't give that momentary
SAC-rate.
Linus