Have you ever come across a situation, when your Xbox fails to connect with the internet connection just before one of your big matches? Well, if yes, then let me tell you I can relate to this situation completely.
Check out, what I did that time:
Restart Your Wi-Fi: Turn off your router, and then turn it on after 20 seconds. Check whether it is working properly on other devices or not.
Restart Your Xbox: Press and hold the power button of your device for 10 seconds to fully restart it.
Try to use a Wired Device: If you are using your Xbox on Wi-Fi, try to use an Ethernet cable for a more stable connection.
Re-enter Your Wi-Fi Details: Open the network section on your device>> setting>> tap on Wi-Fi name>>tap on forget>> re-enter all the details again to reconnect.
Update System Software: Head over to Settings>> System>> Updates. Check the update notification and update your system.
Consequently, after my experience, I can confidently say, that by following the aforementioned steps you will surely be able to resolve your issue shortly.