Without having verified this, I guess you are using the default lower bound of 0. You should add the variables with lower bound -INF.

Best regards,
Thomas

Hi Thomas,

Thanks for the reply. The problem was indeed caused by me not defining lower bound/upper bound. I added the bounds in the add variable section and now it works!

The default upper bound should be +INF, so you should not have to specify it explicitly. But of course, it is perfectly ok to do so.

Best regards,
Thomas