unity2019 Gradle install not valid

There could be a few reasons why you are encountering the error "Gradle install not valid" in Unity 2019. Here are some possible solutions:

1. Make sure that you have installed the correct version of Gradle that is compatible with Unity 2019. You can download the correct version of Gradle from the official Gradle website.

2. Check if your Gradle installation path is correct. In Unity, go to Edit -> Preferences -> External Tools and make sure that the path to your Gradle installation is correct.

3. Try deleting your Gradle cache. In Unity, go to Edit -> Preferences -> Cache and click on "Clear Cache" for Gradle.

4. Check if your system environment variables are set up correctly for Gradle. You can check this by opening a command prompt and typing "gradle -v". If you see an error message, then you may need to add the Gradle path to your system environment variables.

5. Finally, you can try reinstalling Unity and Gradle to see if that resolves the issue.