We use the AxSeriel COM Driver from https://www.activexperts.com/serial-port-component/ . It's a DLL that is placed in the Scripts folder and then used in c#. In the Editor everything works fine but when we create a build we get the NotSupportedException error thrown. The Whole construct worked with the 2018 Version of Unity, after the Update this problem appeared. Code (csharp): System.NotSupportedException: Specified method is not supported. at (wrapper cominterop) AxSerial.ComPortClass..ctor() at MyNamespace.Serial.SerialManager.initComponents () [0x0005d] in C:\Users\MYUSER\Documents\Unity\MYPROJECT\Assets\Scripts\Serial\SerialManager.cs:86 We've tried verious solutions that we found all over the internet loke creating a DLL folder in the Assets root and palce the dll there and alos copy itin the Unity/Editor folder etc. Nothing worked :/ Maybe someone have a Hint/Solution for this problem. Thanks.