As of October 5, 2023, Okta no longer supports RC4_HMAC_MD5 encryption for Agentless Desktop Single Sign-On (ADSSO) and Silent Activation for Microsoft Office 365. Any users in orgs still using RC4_HMAC_MD5 encryption will have their authentication blocked in ADSSO and Office 365 Silent Activation flows.

• Agentless Desktop Single Sign-On (ADSSO) 
• Microsoft Office 365 (O365) Silent Activation

If using ADSSO and Office 365 Silent Activation, update the encryption method from RC4_HMAC_MD5 to one of the alternate, supported encryption methods. Okta recommends using AES 128-bit (AES-128) or AES 256-bit (AES-256) encryption.

To make this change, use a local security policy to change the encryption settings of a single computer or server. Alternatively, implement a group policy to apply the encryption settings to multiple servers or computers in the domain, including domain controllers.

For a detailed guide, please review the article Configuration Steps to Update to AES Due to End-of-Life RC4_HMAC_MD5 Encryption for ADSSO and Silent Activation.