AWS Certified Security - Specialty SCS-C03

A company that uses AWS Organizations uses AWS IAM Identity Center (AWS Single Sign-On) to manage access to AWS accounts. A security engineer is creating a custom permission set in IAM Identity Center. The company will use this permission set across multiple accounts. An AWS managed policy and a customer managed policy are attached to the permission set. The security engineer has full administrative permissions and is working in the management account.

When the security engineer tries to assign the permission set to an IAM Identity Center user with access to multiple accounts, the assignment fails.

What should the security engineer do to resolve this failure?