Incredibuild agent can not assign to build process

[GeorgeHungary]

I got only a short warning during build in VS2010

the helper process was unable to initialize due to an unknown error.
We use incredibuild 5.0 on Windows 7 and windows 10 helper machines. The coordinator is running under Win10.

Also on the warning window there was an line about .net framework is not compatible. every machine has 4.0 and 4.6.1 .net framework installed, so no sense... but somehow only one helper could assign to build which is running windows 7. Any idea what should I try?
http://imgur.com/a/7QWRr

 

[GeorgeHungary]

Somebody?

 

[Colif]

have you asked on here: https://www.incredibuild.com/frequently-asked-questions-technical.html

seems they up to version 7.2, but since I don't anything about this I can't guess if that means anything.