EEG trigger not received when paradigma played at one PC but with the other - Port Problem?

Hallo,
we have a problem since we need a paradigma with EEG trigger to work at a PC where it doesn’t but with another PC it does work. There is no obvious difference between the PC. Other EEG Experiments work perfectly well with the purposed PC. It can’t be the problem of the scripts since it is working at another PC very well, too.
The Question is, what problems could possibly occur with the Port settings? The port we are using is the LPT1.

Thank you for any tips or help!