It happens sometimes. Try reinstalling 

Thanks, but I'm quite sure the problem is that I am temporarily using a VERY strict internet. Sometimes the game will start, but I can never play a battle cuz of the strict filter.

Hello! As N8 _ said, reinstalling can help if your version of the game is missing some of the components after the Update. Otherwise, if the reinstallation doesn't help you, please contact our Support team via https://plrm.me/arena_support or email them at: [email protected]. They will help you!