When upgrading projects, Unity may report that it cannot find the Java Development Kit (JDK) or Android SDK, halting mobile builds.

Changes to Unity's backend authentication servers can sometimes interrupt the older communication protocols used by Hub v2.

Close Unity Hub completely via Task Manager or Activity Monitor. Navigate to your user data folder: Windows: C:\Users\ \AppData\Roaming\UnityHub

Getting Started with Unity Hub 2.4.5: A Guide to the Classic Launcher