The majority of crash issues are resolved by doing a full uninstall. Unfortunately, the game does not always remove the all of its associated files when it is uninstalled. Reinstalling the game while those files are still present can create a conflict within the program and cause it to crash at launch.
Uninstall the game by going to your Windows Control Panel and selecting Programs and Features, selecting "Pokémon Trading Card Game Online" and choosing "Uninstall." Follow the prompts to completely remove the game. Next, follow these steps to ensure that no trace of the game's temporary files remain on your computer:
Go to the Programs and Features section your computer's Control Panel. Select the game and uninstall it.
Go to the directory where the game was installed. The default directory is C:\Users\[your user name]\AppData.
The game stores files in the following folders: LocalLow, Roaming, Unity
Go into the LocalLow folder and delete the "The Pok_mon Company International" folder.
Go into the Roaming folder and delete the "Pokemon Trading Card Game Online" folder.
Delete the "Unity" folder.
Empty your Recycle Bin.
Once you've completed this process, grab the latest installer from
www.pokemontcg.com/download and reinstall the game. As mentioned above, there is a high likelihood that this will resolve your crashing issue.