Some users are complaining that they cannot add their personal Gmail account to their fully managed devices. Why might this be the case?

The most likely reason users cannot add personal Gmail accounts to fully managed devices is that the company's device policy controller (DPC) has been configured to restrict the addition of personal Google accounts. This is a common security and compliance measure in enterprise environments to prevent data leakage and ensure devices are used primarily for work purposes. Android Enterprise is designed to support both company and personal accounts, but administrators have granular control over these settings. The Gmail app version is unlikely to be the sole cause, as older versions typically still allow account additions. Android Enterprise does not inherently limit Google applications to one account; rather, policies dictate such restrictions.