DCD 1.3.1 reports LabelManager 420P IsConnected as false even though it's connected

[fssup]

Info: DCD 1.3.1 on Windows 10 1909 x64 Visual Studio 2019 DYMO.Connect.SDK 1.3.1.115 Installation steps followed from WPFSDKSample

Steps to reproduce:

1. Installation according to WPFSDKSample
2. Create new C# .NET Framework console application in Visual Studio 2019
3. Build this file:

using DymoSDK.Implementations;
using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Threading.Tasks;

namespace PrinterInfo
{
    class Program
    {
        static void Main(string[] args)
        {

            IEnumerable<DymoSDK.Interfaces.IPrinter> Printers;
            Printers = DymoPrinter.Instance.GetPrinters();
            foreach (DymoSDK.Interfaces.IPrinter Printer in Printers)
            {
                Console.WriteLine(Printer.Name + ", IsConnected: " + Printer.IsConnected + ", IsAutoCutSupported: " + Printer.IsAutoCutSupported + ", PrinterType: " + Printer.PrinterType);
            }
            Environment.Exit(0);
        }
    }
}

4. Connect DYMO LabelManager 420P
5. Run the executable you just build from the commandline
6. The SDK reports the LabelManager 420P as IsConnected: False even though it's connected and I can print to it

[EDIT] Even the interface of DCD 1.3.1 now reports the 420P as offline, even though DCD 1.3.1 is completely fine and able to print to it from the interface. Disconnecting, reconnecting, turning off and on the 420P etc has no effect.

[EDIT2] The DYMO MobileLabeler connected to the same system at the same time has no issues and is properly recognized as online.