I have created a project from 0, import steamVR and followed the VRTK asset package, but at the time of playing I get the following error.
PlayerSettings Validation: Requested build target group (27) doesn't exist; #define symbols for scripting won't be added. UnityEditor.PlayerSettings:SetScriptingDefineSymbolsForGroup(BuildTargetGroup, String) VRTK.VRTK_Defines:EnsureVersionSymbolIsSet() (at Assets/VRTK/Scripts/Internal/VRTK_Defines.cs:60) UnityEditor.EditorAssemblies:ProcessInitializeOnLoadAttributes()
The VRTK asset package from the Asset store is not up to date in order to work with the latest version of Unity. That's why you are getting that error.
You have to install the latest version from Github which is actively updated. You can find the official SDK from here. Make sure to remove the old one first.