Requesting Assistance on Master Audio Errors after Upgrading

Dear DarkTonic Dev,

I just upgraded from Unity version 2019.2.19f1 to version 2019.4.3f1 and now have a number of errors as follows:

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Settings\DynamicGroupVariation.cs(4,19): error CS0234: The type or namespace name 'AddressableAssets' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Settings\MusicSetting.cs(6,19): error CS0234: The type or namespace name 'AddressableAssets' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Settings\SoundGroupVariation.cs(5,19): error CS0234: The type or namespace name 'AddressableAssets' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(6,19): error CS0234: The type or namespace name 'AddressableAssets' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(7,19): error CS0234: The type or namespace name 'ResourceManagement' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Utility\PlaylistController.cs(7,19): error CS0234: The type or namespace name 'AddressableAssets' does not exist in the namespace 'UnityEngine' (are you missing an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Settings\MusicSetting.cs(22,16): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Settings\DynamicGroupVariation.cs(33,16): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(40,74): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(123,54): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(145,57): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(179,47): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)
Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(191,106): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(256,59): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(266,56): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(276,48): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Settings\SoundGroupVariation.cs(38,16): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(15,16): error CS0246: The type or namespace name 'AsyncOperationHandle<>' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Singleton\AudioAddressableOptimizer.cs(21,35): error CS0246: The type or namespace name 'AsyncOperationHandle<>' could not be found (are you missing a using directive or an assembly reference?)

Assets\Plugins\DarkTonic\MasterAudio\Scripts\Utility\PlaylistController.cs(103,50): error CS0246: The type or namespace name 'AssetReference' could not be found (are you missing a using directive or an assembly reference?)

I have tried removing Master Audio completely from my project and everything works again when I do but of course I lose all the Master Audio sounds.

Re-importing Master Audio from the Unity Store brings back the same problem and errors as listed above.

Hoping you can help or assist with a solution for this.

Kind regards,

DL