The Taylor v1.51 software is probably not capable of supporting the Quantum 434. I thought that the Modsoft v2.6 did support it.
Both of your software packages are DOS based so they worked okay upto WIN95. The Taylor license for Modicon 984LL was purchased by Schneider Electric (the guys that also bought Modicon), and all of their Windows based products support the 434.
Maybe it is time for you to purchase software for the 21st century.