After pausing the simulation, I click on a facet on a pipe and turn on the u,v vectors on 3d viewer settings. I then change the profile category to display "pressure along u" in the facet settings.
After this, I go to the tools tab and open up the profile plotter. And I click on the downward arrow of the box and nothing expands.
Any help is appreciated. 
Can you try two things quickly?
- This may sound obvious, but just to be sure: after you set "pressure along u", do you click Apply in the facet settings pane?
- Does maybe closing and reopening the Profile Plotter window help?
That did it!
Sorry, the quick start guide does not say that you must apply the facet profile prior to running the simulation. If you press apply after you have begun running the simulation, it states that the simulation will be reset.
Thanks again.
Molflow can have very big systems with 100.000+ facets. It would be very inefficient to count profiles (3*100 values for steady state, more for time-dependent simulations) on each of them.
That's why - as a compromise - the user can set up profiles on any facet but he has to do it before the simulation starts. That way memory is allocated only as needed. As a consequence, yes, the simulation needs to be reset if a profile property is changed after it begun.
Glad the problem was solved.