Error Running Connect-ExchangeOnline Command in C# using ExchangeOnlineManagement PowerShell Module

Question

I'm attempting to connect to Exchange Online using Exchange Online PowerShell V2 in C# using the Connect-ExchangeOnline command from the ExchangeOnlineManagement module. My code looks like this:

    public class EMShell : IDisposable
    {
        public PowerShell EXOShell { get; set; }

        public EMShell()
        {
            InitialSessionState iss = InitialSessionState.CreateDefault();

            iss.ImportPSModule(new string[] {"ExchangeOnlineManagement" });

            iss.ExecutionPolicy = Microsoft.PowerShell.ExecutionPolicy.RemoteSigned;

            iss.ThrowOnRunspaceOpenError = true;

            Runspace runspace = RunspaceFactory.CreateRunspace(iss);

            runspace.Open();

            EXOShell = PowerShell.Create(runspace);

            var credentialsPath = Settings.Default.Credentials;

            EXOShell.Commands.Clear();

            EXOShell.AddCommand("Import-Clixml");

            EXOShell.AddParameter("Path", credentialsPath);

            var cred = EXOShell.Invoke().First();

            var credentials = new PSCredential(cred);

            EXOShell.Commands.Clear();

            EXOShell.AddCommand("Connect-ExchangeOnline");

            EXOShell.AddParameter("Credential", credentials);

            var res = EXOShell.Invoke();
        }

        public void Dispose()
        {
            EXOShell.Commands.Clear();
            EXOShell.AddCommand("Disconnect-ExchangeOnline");
            EXOShell.AddParameter("Confirm", false);
            EXOShell.Runspace.Close();
        }
    }

When I run this code, I get the following error on line var res = EXOShell.Invoke();:

System.Management.Automation.CommandNotFoundException: "The 'Update-ModuleManifest' command was found in the module 'PowerShellGet', but the module could not be loaded. For more information, run 'Import-Module PowerShellGet'."

This is strange because the Update-ModuleManifest command belongs to the PowerShellGet module and I wouldn't expect it to be required for the Connect-ExchangeOnline command.

Interestingly, the Connect-ExchangeOnline command runs fine in the PowerShell console without needing to load the PowerShellGet module.

I have already checked that both the ExchangeOnlineManagement and PowerShellGet modules are properly installed on my system.

Can anyone explain why this error is occurring and how I might fix it? Is there a dependency between the Connect-ExchangeOnline command and the PowerShellGet module that I'm overlooking?