Thanks for reaching out to the Speakers and Displays Community forum. We'd love to help.
A few questions: were you able to receive calls on your Google Nest Hub before? If yes, when did this issue start? Have you tried any troubleshooting steps?
Google Nest Hub and other Google Nest devices can only receive video calls made using Google Meet or Zoom and carrier calls made using Google Fi, Google Voice, Taiwan Mobile, Telecom Italia or Telstra. If your carrier is not among these providers, then accepting incoming calls is not supported on your end. Check out this support website for more information.
Keep me posted.