iOS build failing: Unhandled Exception: System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.

iOS build fails with the following stack. Using 5.4.0.f3 and latest IAP API. Toggling services did not help.

Unhandled Exception: System.Reflection.ReflectionTypeLoadException: The classes in the module cannot be loaded.

at (wrapper managed-to-native) System.Reflection.Assembly:GetTypes (bool)

at System.Reflection.Assembly.GetTypes () [0x00000] in :0

at Mono.CSharp.RootNamespace.ComputeNamespaces (System.Reflection.Assembly assembly, System.Type extensionType) [0x00000] in :0

at Mono.CSharp.RootNamespace.ComputeNamespace (Mono.CSharp.CompilerContext ctx, System.Type extensionType) [0x00000] in :0

at Mono.CSharp.GlobalRootNamespace.ComputeNamespaces (Mono.CSharp.CompilerContext ctx) [0x00000] in :0

at Mono.CSharp.Driver.LoadReferences () [0x00000] in :0

at Mono.CSharp.Driver.Compile () [0x00000] in :0

at Mono.CSharp.Driver.Main (System.String args) [0x00000] in :0

The following assembly referenced from C:\Users\cbdev\Documents\Unity\Drill1-535\Assets\Plugins\UnityPurchasing\Bin\Stores.dll could not be loaded:
Assembly: UnityEngine.Purchasing (assemblyref_index=1)
Version: 0.0.0.0
Public Key: (none)
The assembly was not found in the Global Assembly Cache, a path listed in the MONO_PATH environment variable, or in the location of the executing assembly (C:\Users\cbdev\Documents\Unity\Drill1-535\Assets\Plugins\UnityPurchasing\Bin).

Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class UnityEngine.Purchasing.IAmazonExtensions could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class UnityEngine.Purchasing.IAmazonExtensions could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class UnityEngine.Purchasing.IGooglePlayConfiguration could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class UnityEngine.Purchasing.ISamsungAppsExtensions could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class UnityEngine.Purchasing.ISamsungAppsExtensions could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class UnityEngine.Purchasing.NativeJSONStore could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class UnityEngine.Purchasing.IAppleConfiguration could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class UnityEngine.Purchasing.IAppleExtensions could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class DialogType could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class StoreInstance could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class MicrosoftConfiguration could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class UnityEngine.Purchasing.FakeStore could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class DialogRequest could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class LifecycleNotifier could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
Could not load file or assembly ‘UnityEngine.Purchasing, Version=0.0.0.0, Culture=neutral, PublicKeyToken=null’ or one of its dependencies.
The class UnityEngine.Purchasing.NativeJSONStore could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class UnityEngine.Purchasing.ITizenStoreConfiguration could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey0 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey0 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey1 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey0`1 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey0 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey1 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey2 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey3 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null
The class c__AnonStorey4 could not be loaded, used in Stores, Version=1.0.6086.27179, Culture=neutral, PublicKeyToken=null

Turns out that reimport and IAP services toggling separately had no effect, but reimporting AND toggling IAP service seems to have fixed the issue.