Yes, you can activate multiple TVs with hbomax/tvsignin. To do so, ensure each TV is connected to the internet and has the HBO Max app installed. Open the app on each TV and sign in using your HBO Max account credentials. The app will display a unique activation code for each device. Visit hbomax/tvsignin on your computer or mobile device, enter the code, and follow the prompts. Repeat this process for each TV. Keep in mind that the number of simultaneous streams may be limited depending on your HBO Max subscription plan, so check your account for details.