Google.Protobuf.dll is right next to my .dll but it is not being found or loaded

I have a Framework 4.8 C# app that uses ClearScript to allow JavaScript to be used as an extension language. I am able to write plugins as DLLs and attach them at runtime, viz

JSE.Script.attach = (Func<string, bool>)Attach; ...         private static bool Attach(string dllPath, string name = "")         {             var status = false;             var htc = new HostTypeCollection();             try             {                 var assem = Assembly.Load(AssemblyName.GetAssemblyName(dllPath));                 htc.AddAssembly(assem);                 if (name.Length == 0)                 {                     name = assem.FullName.Split(',')[0];                 }                 JSE.AddHostObject(name, htc); //FIXME checkout the hosttypes                 Console.Error.WriteLine($"Attached {dllPath} as {name}");                 status = true;             }             catch (ReflectionTypeLoadException rtle)             {                 foreach (var item in rtle.LoaderExceptions)                 {                     Console.Error.WriteLine(item.Message);                     T.Fail(item.Message);                 }             }             catch (FileNotFoundException fnfe)             {                 Console.Error.WriteLine(fnfe.Message);                 T.Fail(fnfe.Message);             }             catch (Exception e)             {                 Console.Error.WriteLine(e.Message);                 T.Fail(e.Message);             }             return status;         } 

This permits my scripts to have lines like

attach(".\\Plugin_GoogleAds_Metrics.dll"); H = Plugin_GoogleAds_Metrics.GoogleAds_Metrics.Historical; H.EnableTrace("GAM"); ... 

I've made a public repo of the plugin for those interested.

What's not working in this situation is that when I try to execute the plugin's GetAccountInformation method, and execution reaches the GoogleAdsServiceClient googleAdsService = client.GetService(Services.V11.GoogleAdsService); line, an error is thrown complaining about Google.Protobuf, viz

Exception has been thrown by the target of an invocation.     at JScript global code (Script [23] [temp]:5:0) -> acc = H.GetAccountInformation(auths.Item1, 7273576109, true)    at Microsoft.ClearScript.ScriptEngine.ThrowScriptError(IScriptEngineException scriptError)    at Microsoft.ClearScript.Windows.WindowsScriptEngine.ThrowScriptError(Exception exception)    at Microsoft.ClearScript.Windows.WindowsScriptEngine.<>c__DisplayClass57_0`1.<ScriptInvoke>b__0()    at Microsoft.ClearScript.ScriptEngine.ScriptInvokeInternal[T](Func`1 func)    at Microsoft.ClearScript.ScriptEngine.ScriptInvoke[T](Func`1 func)    at Microsoft.ClearScript.Windows.WindowsScriptEngine.ScriptInvoke[T](Func`1 func)    at Microsoft.ClearScript.Windows.WindowsScriptEngine.Execute(UniqueDocumentInfo documentInfo, String code, Boolean evaluate)    at Microsoft.ClearScript.Windows.JScriptEngine.Execute(UniqueDocumentInfo documentInfo, String code, Boolean evaluate)    at Microsoft.ClearScript.ScriptEngine.Evaluate(UniqueDocumentInfo documentInfo, String code, Boolean marshalResult)    at Microsoft.ClearScript.ScriptEngine.Evaluate(DocumentInfo documentInfo, String code)    at Microsoft.ClearScript.ScriptEngine.Evaluate(String documentName, Boolean discard, String code)    at Microsoft.ClearScript.ScriptEngine.Evaluate(String documentName, String code)    at Microsoft.ClearScript.ScriptEngine.Evaluate(String code)    at RulesetRunner.Program.Run(JScriptEngine& jSE, String scriptText, Config cfg, Dictionary`2 settings) in C:\Users\bugma\Source\Repos\Present\BORR\RulesetRunner\RunManagementPartials.cs:line 72 Exception has been thrown by the target of an invocation. Exception has been thrown by the target of an invocation. Could not load file or assembly 'Google.Protobuf, Version=3.15.8.0, Culture=neutral, PublicKeyToken=a7d26565bac4d604' or one of its dependencies. The system cannot find the file specified. 

So

1. I am using the latest Google.Ads.GoogleAds library
2. AutoGenerateBindingRedirects has been set to true in the csproj file
3. Add-BindingRedirect has been executed in the context of the Plugin's project
4. The Plugin_GoogleAds_Metrics.dll is in the same folder as the Google.Protobuf.dll

Where to from here?