What is the issue:

Apple sometimes updates the macOS, iOS, iPadOS, or tvOS Software License Agreement, often when releasing a new OS version. When a Software License Agreement is updated, an Apple Business Manager Administrator must log into the program website to review and agree to the updated terms.

From Apple:

If Apple Business Manager, Apple Business Essentials, or Apple School Manager asks you to approve new terms and conditions
Important issues that occur until the updated agreement is accepted:
  • In Apple Business Manager, you can’t assign new devices to your MDM server, even if you have selected the option to automatically assign new purchases to a specific MDM server.
  • Your MDM server might report an error message like "403 T_C_NOT_SIGNED” when communicating with Apple’s device management servers.

The message on Jamf Pro:

Steps to approve a new agreement:

  1. Log in to Apple Business Manager with an administrator-role user
  2. The new Terms and Conditions should pop up
  3. Mark the two relevant checkboxes
  4. Click the Agree button
  5. Check Jamf Pro Again after 5-15 minutes to make sure the warning is cleared