PDE solve block not working per support page

I am using Mathcad Prime Release 9.0 and Datecode9.0.0.0

Using the support page https://support.ptc.com/help/mathcad/r9.0/en/#page/PTC_Mathcad_Help/partial_differential_equations_in_solve_blocks.html#wwID0EQ5E6

The following solve block should work (// denotes beginning of new line, and | denotes limits of solve block):
|
// u(0,t)=0
// u(x,0)=s(x*pi)+1/2*sin(x*3*pi)
// u.t(x,t)=1/4*u.xx(x,t)-1/2*u.xx(x,t)
// pdesolve(u,x,[0],t,[0],10,10)
// [1] [1]
|

where the following is intended to represent a 1x2 matrix:
// [0]
// [1]

Instead there is an error message: "this value must be a function"

Here are the errors that I faced
"this value must be a function" error when attempting to use pdesolve in the above context.