Cannot install python for unity package 4.0.0-exp.5

Hi,

I was trying to install the python for unity 4.0.0-exp.5, and meet the installation requirements. But during the installation process, I got this error that 1 package cannot be found:

PythonInstallException: Python for Unity: Unable to add package [com.unity.scripting.python.windows@1.0.0-exp.3]:
Package [com.unity.scripting.python.windows@1.0.0-exp.3] cannot be found
Please check the Python for Unity package documentation for the install troubleshooting instructions.
UnityEditor.Scripting.Python.PythonRunner.InstallPython () (at Library/PackageCache/com.unity.scripting.python@4.0.0-exp.5/Editor/PythonRunner.cs:612)
UnityEditor.Scripting.Python.PythonRunner.InstallAndLoadPython () (at Library/PackageCache/com.unity.scripting.python@4.0.0-exp.5/Editor/PythonRunner.cs:403)
UnityEditor.Scripting.Python.PythonRunner.DoEnsureInitialized () (at Library/PackageCache/com.unity.scripting.python@4.0.0-exp.5/Editor/PythonRunner.cs:681)
UnityEditor.Scripting.Python.PythonRunner.EnsureInitialized () (at Library/PackageCache/com.unity.scripting.python@4.0.0-exp.5/Editor/PythonRunner.cs:325)
UnityEditor.EditorApplication.Internal_CallDelayFunctions () (at <d6a6a4b561b9431dbfe2c61f7bf0d405>:0)

I installed python3.7 manually, but this error still appear. I searched in forum and Google, but seems like no one has similar problem. Also, the install troubleshooting instructions mentioned above cannot be found.

Is there any solution for this error? Any help is appreciated!

I'm using Unity version 2020.3.2f1 on a free personal license, with MRTK2.7.2, openXR1.0.0, and OptiTrack plugin 1.2.0