Hey there MonicaErickson,
If you haven't already, try deleting the car key from your iPhone, then add it back to test and see if that helps. Use the steps from the resource you came to us from, linked below to remove and add it back:
1. On your iPhone, open the Wallet app.
2. Tap your car key.
3. Tap the More button
.
4. Find the option you need:
• To share, tap invite and follow the instructions.
• To revoke a shared key, tap the person's name and follow the instructions.
• To delete a key from the Wallet app, tap Remove Key.
How to add your car key to Apple Wallet on your iPhone
1. Make sure that your car is associated with the account provided by the car's manufacturer.
2. Open the car manufacturer's app, email, or text message, or use your car's display and follow the instructions to set up a key.
3. When you're sent to the Wallet app, tap Continue.
4. If prompted by the onscreen instructions, place your iPhone on the key reader while your iPhone and car pair.
5. When your iPhone and car finish pairing, tap Done.
When you add your car key on your iPhone, it might be added automatically to your paired Apple Watch. Or you might see the option to add it to your paired Apple Watch.
You can also manually add your car key to your Apple Watch. In the Apple Watch app on your paired iPhone, tap Wallet & Apple Pay > the Add button next to your car key.
For more info: Add your car key to Apple Wallet on your iPhone or Apple Watch - Apple Support
Take care!