Compiling doesnt work on VS2015 Professional Edition 

I have recently installed the LESS COMPILER on my VS 2015 and 2017 PRO copies. Sadly neither works. extension 0.9.44 is installed on both VS versions. 

configuration is 

Project: On 
File: On 

Neither works on saving the file nor on compiling from the solution file. 

Any help is appreciated. 