Trial mode will load the scenery for 5 minutes at time, and it will say the "Trial for xxxx has started" when you go there. When you don't see any buildings at an airport, you are NOT in Trial mode, you have a problem with the software modules not starting.
Sometimes, it's possible that if you closed a previous session of the sim and opened a new one very quickly, the system couldn't close all files and shut down all started executables from the previous session, so they would be unavailable for the next one. The installer will also automatically close all executables still running, which explains why reinstalling fixed it.