As per the title - I have 3DS Max 2021.
I also have some plug-ins, including Verge3D.
I installed your D5 to trial it and upon starting up 3DS Max, I was getting greeted everytime by an error message dialog box complaining about Verge3D.
So I contacted the authors of Verge3D, told them that this error has begun happening due to the install of D5 and they said “it is possible that this plugin clutters the environment variables somehow”, and they suggested I try changing the ADSK_3DSMAX_PYTHON_VERSION (in System Properties, via the “edit the system environment variables” search).
That version was set to 2 and it was suggested it should be 3, and to try that.
I changed that variable but now I have an error which they claim is a D5 error and to notify yourselves.
Here is the new error message I now get;