The Mathcad try version I have just downloaded does not have symbolic features, which I used in MathCad 14.

Did you buy a license for Prime? Then activate that license: Go to the Circle M in the upper left corner, then select “Options” and choose the “License” tab. Then browse to your license file.

Did you not buy a license? Then opt for a 30 day trial to use the full functionality: On the same form as above, instead of browsing to your license file, select the  ‘Get License’ button and follow the steps. Note that after 30 days, your Prime will fall back to express mode, unless you (buy and) activate a license in the mean time.

Success!
Luc