Salesforce Opportunity Visibility Issue After User Deactivation and Reactivation

Universal Containers utilizes a private sharing model for Opportunities and relies on Opportunity teams. Criteria-based sharing rules are not employed. A sales representative at Universal Containers departed the company, leading to the deactivation of their user record. Subsequently, the representative was rehired in the same role. The administrator activated the old user record and added the user back to the same default Opportunity teams. However, the user is unable to access the same Opportunities they previously worked on before leaving the company.

What is the likely cause of this issue?