Check and see if it was installed in the Microsoft Flight Simulator\Community folder. When I install a product from Captain Sim for MSFS2020, I actually use this method:

Where the product was bought from, I select Other
Then it asks me to browse for the MSFS2020 installation (in my case E:\Flight Sims\Microsoft Flight Simulator)

Now.... If I select E:\Flight Sims\Microsoft Flight Simulator, I can't see it in the sim. In other words, it doesn't install in the E:\Flight Sims\Microsoft Flight Simulator\Community folder. I must browse to E:\Flight Sims\Microsoft Flight Simulator\Community folder in order for it to install in the actual Community folder, and not just into the Microsoft Flight Simulator folder where it won't show in MSFS2020!