Laptops can be problematic.
Battery management software can cause hang-ups and other problems. Low power/low voltage LPT ports may not drive the break out boards adequately - the low voltage signals are also more susceptible to noise than a regular 5v system.
A number of Mach users will contend that laptops are not the best choice for use with Mach. Yet, others will say that a laptop is just fine.
The subject was discussed fairly deep in one of these threads but I can't recall which one:
FINALLY started BIG_CNC_LATHE conversion NC Controller difference Interest in Lathe retrofit
Although the threads involve lathes, the Mach laptop issue would pertain no matter what the machine.
You might want to check out the Mach support site - surely this question has been posed and answered any number