Exception:

“You can only forward records that you or your subordinates own. System administrators can forward all records.”

Resolution:

This is an expected exception or error when an user tries to share records that are owned by user above them in the role hierarchy. System administrators can share all records in Salesforce to Salesforce. But, non-system administrator users can only forward the records that they (or their subordinates in the role hierarchy) own.

Reference Article:

https://help.salesforce.com/s/articleView?id=sf.business_network_tips.htm&type=5