Hello technicallyimparied,
Thanks for reaching out to the Apple Support Communities. From your message it looks like the incoming call is hanging up after one ring, and you're unable to answer it on your iPhone.
If this is accurate, begin with the troubleshooting steps below. If any of the steps resolve the issue you don't need to continue working through them:
1 - Restart your iPhone.
2 - Restart your Mac: Go to the Apple menu in the top left corner of your screen > Restart.
3 - Once both have restarted, see if the issue persists.
4 - If the issue persists, can you answer the call from the MacBook?
5 - Turn off the settings on your Mac to receive calls: Make and receive calls on your Mac, iPad, or iPod touch. Are you able to answer them from your iPhone with this feature off?
6 - If you can answer the calls when the feature is turned off, create a new user on your MacBook: How to test an issue in another user account on your Mac.
7 - Set up the feature from the new user and see if there is any change: Make and receive calls on your Mac, iPad, or iPod touch.
All the best.