yes. it's probably because you haven't created an online character yet. to import your custom MP character you need to have a character TO import in the first place. if it still happens even though you have an MP character, then I don't know why it's happening.
the only issue I have with the trainer is that, while there is an option to add money, there is no option to change the amount of money you add per activation. no values to change in the configuration file, so you'll have to press the button 1000 times to get 10k.
is it possible to add John's hair to the hair components? or just Arthur's long hair? or an ability to change the color of your hair? I also noticed that most of the multiplayer outfits don't have clothing physics, or they have a minimal amount of it. is it possible to change that?