Is it possible that the crash detection page stays on screen after tapping on cancel button?

Thanks so much for visiting the Apple Support Communities yilun33,

The Crash Detection screen should turn itself off when selecting the Cancel button. If it does not, we would recommend trying to force restart your watch. This step can be taken to restart an unresponsive device, which it sounds like you may be experiencing. To learn how, see the "Force restart your Apple Watch" section of the Apple Support article Restart your Apple Watch - Apple Support.

For more details on how Crash Detection works, we would suggest referencing the Apple Support article you found your way to the communities from, Use Crash Detection on iPhone or Apple Watch to call for help in an accident - Apple Support.

And if you still need help after that, please get in touch with Apple Support directly. They will have the tools and resources needed to further assist. You can do that here: Get Support.

Have a wonderful day!