Hello Kayles187,
If the Calendar widget is not working properly, you'll want to cover the basics first. Restart the device, and if you're still using the original version of iOS 16 make sure you have updated to the current version, 16.0.2.
Restart your iPhone
Update your iPhone
You can also try removing and re-adding the widget to the Lock Screen.
- Touch and hold the Lock Screen until the Customize button appears at the bottom of the screen, then tap Customize.
2. Tap Customize, then tap the box below the time to add widgets to your Lock Screen.
3.. Tap on the Calendar widget then select the minus button above it to remove it.
4. Select the Calendar widget from the Add Widgets list to add it back.
Personalize your iPhone Lock Screen
If the Calendar widget is still not working, you'll want to contact Apple to report that issue: Get Support
Cheers!