Unable to list target platforms. Build SDK trouble.

Hello. I’m having a problem with Unity when a try to compile a project to Android. I have changed the SDK directory several times, but this doesn’t work, Unity still showing the message “Please make sure the Android sdk path file is correct”. Can someone help me, please? Thank you for your attention.
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Does this thread help? https://forum.unity3d.com/threads/unity3d-5-5-0fx-unable-to-list-target-platforms-error.446096/