I had same problem. After installing new modules, i did not get the activation for a10 module.
Try activate A10 module in Program Files/DSC: World/Mods/aircrafts/a-10/bin/a10_protect.exe
That happend when A10 module is not activated. Try delete A10 folder from mods/aircrafts and install modul again, after install check Start game and click on Finish.