@a_block Thanks Andreas for the head up, by using the demo versions i was at least able to port the plugins to r18 in the past, which seemed to work even in r19, at least that is what a customer told me. with the r20 demo i couldn't even open up the sdk example. and exactly that is what prevents me from going on, since i am not able to find the issue, why it doesn't work. i don't even know where to start looking. and i am quite sure that my computer is the cause since it is quite old and the system may be a total mess due to those millions of installations and deinstallations i did over the years.
i am trying to install the demo and visual studio on a friends computer to see if it gives positive results.
edit: going thru the steps Donovan wrote. Seems to get me on track... so thanks again for the input