I already sorted this out for myself, but i am adding my issue for others in the future since this thread came up when i was searching for answers.
If your profile name has a space in it, you need to enclose it with quotation marks or it only recognizes the first word and tries to load a non existent profile.
Example- My custom profile is named Boss CNC. The shortcut path that worked for me is C:\Mach4Hobby\Mach4GUI.exe /p "Boss CNC"
I just experimented until i found something that worked. Perhaps this would be common sense to most users, but I wanted to document it just in case.
Thanks!