Hey there, let's break down these frustrating issues one by one—Unity's module management can be finicky with older LTS versions, but we'll get you sorted.

First: Resolve the "Unity version is already located by the hub" error #

This usually pops up when Unity Hub doesn't recognize your 2019.4.13f1 installation as a "managed" instance (so you can't add modules directly through the Hub). Try this fix:

• Unlocate and re-add your installation:
  1. Open Unity Hub, go to the Installs tab.
  2. Find your 2019.4.13f1 entry, click the three-dot menu, and select Remove from Hub.
  3. Click Add > Locate, then navigate directly to your Unity 2019.4.13f1 installation folder (typically C:\Program Files\Unity\Hub\Editor\2019.4.13f1 or your custom path).
  4. Once re-added, the Hub should mark it as a managed installation, and you'll see the Add Modules option when you click the three dots again.

Second: Fix the "Failed to locate unity.exe" error with the standalone installer #

If the module installer can't find your Unity executable, it's almost always a path mismatch or permission issue:

• Run the installer as Administrator: Right-click the installer file, select Run as administrator—this avoids permission blocks that might stop it from accessing the Unity folder.
• Manually point to unity.exe: When the error appears, look for a Browse or Locate option. Navigate to your 2019.4.13f1 folder, select Unity.exe (it's in the root of the installation folder), and proceed.
• Check for special characters in your path: Unity installers hate spaces, accents, or special symbols in folder names. Stick to simple paths like C:\Unity\2019.4.13f1 instead of C:\My Unity Projects\2019.4.13f1.

Third: Ensure the Android module loads correctly after installation #

Once you've got the module installed, double-check these steps to make Unity recognize it:

• Restart everything: Close all Unity instances and Unity Hub, then reopen Hub and launch your project.
• Verify module status in Hub: Go back to the Installs tab, click the three dots on your 2019.4.13f1 entry, select Add Modules—you should see the Android module marked as installed.
• Refresh Build Settings: Open your project, go to File > Build Settings, switch to Android. If the error still shows, click the Refresh button at the bottom of the window.
• Set up Android SDK/JDK manually (if needed): Unity 2019 LTS might require you to point to SDK/JDK paths. Go to Edit > Preferences > External Tools, and use the paths installed with the Unity Android module (usually C:\Program Files\Unity\Hub\Editor\2019.4.13f1\Editor\Data\PlaybackEngines\AndroidPlayer\SDK).

If all else fails, a clean reinstall is a reliable last resort: Uninstall Unity 2019.4.13f1 (and all its modules) via Hub, then reinstall it fresh with the Android module selected during setup. This fixes weird path or registry glitches that can linger.

内容的提问来源于stack exchange，提问作者swastika pallai