Hi! Thanks for reaching out about the unusual small login window on your PC when trying to access Tennis TV and the "not authorized" issue. That definitely sounds odd. To help you better, could you tell me a bit more:

- Are you accessing Tennis TV through a web browser or a dedicated app on your Windows 10 PC?
- When exactly does this small window pop up—right after you click login or at some other point?
- Does this window look like an official Tennis TV login prompt, or does it look suspicious or unfamiliar?
- Have you tried entering your login credentials there, and did it always say “not authorized,” or did you get any error codes?
- Are you seeing this issue only on this PC or other devices too?

This info will help me understand if this might be a legitimate login prompt from Tennis TV or potentially a phishing or security issue. Meanwhile, here are some quick tips:

1. Ensure you are logging in on the official Tennis TV site or app, not through any third-party or pop-up windows. Sometimes, phishing attempts use small windows to trick users.
2. Clear your browser cache and cookies if you are using a browser. This can fix weird login glitches.
3. Try logging in from another browser or device to see if the same issue happens.
4. Double-check your subscription status on Tennis TV to confirm your account is active.

Once you provide a bit more detail, I can guide you through targeted troubleshooting. If it looks like a security concern, I’ll help you secure your account and report the issue appropriately.

Looking forward to your response!