snapchat not working on iphone 8

Try a forced restart, if that doesn't work uninstall then reinstall Snapchat. If that doesn't work, contact Snapchat as this is not an Apple product.

Try a forced restart.

• Press and quickly release the volume up button

• Press and quickly release the volume down button

• Press and hold the side button.

• When the Apple logo appears, release the button.

https://support.apple.com/en-in/guide/iphone/iph8903c3ee6/ios

my iPhone 8 doesn’t let me use Snapchat it keeps saying no internet connection when my phone is connected to Internet and all my other apps work

You're not alone, this is an issue that seems to have affected several social media apps recently. I don't have an answer but check back later, hopefully someone will be able to answer this.