Take into account that marshallers appear once you have an assigned parking spot or gate after taxing. So you need to go to the one assined by ATC (you can enable the taxi ribbon to double check that). Also remember that not all aircraft may trigger marshallers. There´s a config entry in the aircraft to disable them and for some reason some third party liveries disable that. To be sure take the stock 747 and test it in a big airport like LEMD as this combination will trigger them in 99% of the parking spots/gates. I frequently use that airport and they work at the main terminals or at the satellite terminal. Just spawn on the runway and move to the terminals requisting taxi to ATC.
If you never see them, even on big airports, then you may have an addon with faulty ground services. Most likely it´s an uncompiled services file. This will disable the ground system overally in all airports, except in the ones that have a custom and correct ground services definition.
I reported some of those airports to the authors and they have fixed some of them as well. Check the following topics to know how to fix this manually till it´s patched:
Make a quick search on Community and OneStore folders for something like “Services.xml”, “Services.xml.txt”, “Services.txt” or “Services.zip”. They are the typical errors. Anything else than “Services.spb” (the compiled one) will produce this error.
Cheers