Hello karlie38,
Thank you for participating in the Apple Support Communities! We understand that you're not receiving WhatsApp notifications after updating your iPhone to iOS 15.1. We'd be happy to help point you towards a resolution.
Let's start by checking your Notification settings for WhatsApp on the iPhone to ensure they are not muted or turned off. If you have Do Not Disturb or Focus enabled, you'll want to turn that feature off temporarily to see if you receive WhatsApp notifications with it off:
After that, we'll want to also ensure that Notifications have been enabled in the WhatsApp app itself:
WhatsApp Help Center - How to manage your notifications
Keep us posted with what you find.
Cheers!