Error by building android apk

Hello friends,

(sorry for bad english)

I have a litle problem in my projekt

ad the begining everythings fine… when i cklick build than i become 2 errors

Fierst Error

ArgumentException: The Assembly ChannelPurchase is referenced by Stores (‘Assets/Plugins/UnityPurchasing/Bin/Stores.dll’). But the dll is not allowed to be included or could not be found.
UnityEditor.AssemblyHelper.AddReferencedAssembliesRecurse (System.String assemblyPath, System.Collections.Generic.List1 alreadyFoundAssemblies, System.String[ ] allAssemblyPaths, System.String[ ] foldersToSearch, System.Collections.Generic.Dictionary2 cache, BuildTarget target) (at C:/buildslave/unity/build/Editor/Mono/AssemblyHelper.cs:142)
UnityEditor.AssemblyHelper.AddReferencedAssembliesRecurse (System.String assemblyPath, System.Collections.Generic.List1 alreadyFoundAssemblies, System.String[ ] allAssemblyPaths, System.String[ ] foldersToSearch, System.Collections.Generic.Dictionary2 cache, BuildTarget target) (at C:/buildslave/unity/build/Editor/Mono/AssemblyHelper.cs:148)
UnityEditor.AssemblyHelper.FindAssembliesReferencedBy (System.String[ ] paths, System.String[ ] foldersToSearch, BuildTarget target) (at C:/buildslave/unity/build/Editor/Mono/AssemblyHelper.cs:179)
UnityEditor.HostView:OnGUI()

second Error

UnityEditor.BuildPlayerWindow+BuildMethodException: Build failed with errors.
at UnityEditor.BuildPlayerWindow+DefaultBuildMethods.BuildPlayer (BuildPlayerOptions options) [0x001b9] in C:\buildslave\unity\build\Editor\Mono\BuildPlayerWindowBuildMethods.cs:162
at UnityEditor.BuildPlayerWindow.CallBuildMethods (Boolean askForBuildLocation, BuildOptions defaultBuildOptions) [0x00050] in C:\buildslave\unity\build\Editor\Mono\BuildPlayerWindowBuildMethods.cs:83
UnityEditor.HostView:OnGUI()

hope someone can help me.

thanks

try this:
https://forum-old.unity3d.com/threads/solved-cant-build-apk-using-iap.486925/#post-3192584