Hi there.
Did you get the Silver or Gold Bundle? (Bundle = includes the Toneport DI)
or
Did you get just the download? (just download and "install on your existing line6 hardware")
Please specify how you are using the plugin, what line6 HW you've got if you got one.
Here are some instructions, not full, just the ones I know, coz I've got myself a question.
For Bundle versions (with a hardware or dongle - called Toneport DI)
1) You need the "Dongle" connected (any piece of hardware where the plugin is installed)
2) When you activate the Line 6 Gearbox plugin in the Monkey (check if it's installed by looking at the tab "Optional software or Optional Add ons" (can't recall well now) and it has to be checked and in green, if the gearbox Plugin is checked, great, no more stuff to do here. Otherwise, you need to activate the plugin via Monkey.
3) Open Riffworks, and at the bottom of the window, "deselect" the button "Hardware" (it must go off, no red light" and activate the button (right below the button hardware) "Software" (it must be highlited in red, as a led; which is on)
4) Go to where it says "AMP" and click the the arrow (triangle) pointing down, you'll see Amplitube (if you have installed) and "Other" or it might say "Gearbox", Go to Other and select Gearbox Stereo
Now you're good to go. It's the same procedure that you do when you want to use Amplitube Live (or LE) and/or any VST that you might have installed.
Notes:
- Gearbox Plugin is used the EXACT same way as Gearbox Standalone, therefore I gave you instructions to make it work, rather than who you can use it, mostly because it's up to the taste of the VST owner. For more info using Gearbox, you should read Line'6 Gearbox Manual where you can download directly from Line6.
- Pay attention where is you "plugin path", when you select the software button (after deselecting the hardware button" and clicking on the arrow (triangle pointing down) on the AMP button, you should see a text that says "select pluging path", look at it and see if the Gearbox DLL is there - there is usually a folder that says Line6 or Gearbox, and within the folder you have to see:
Gearbox Stereo.dll
Gearbox Mono.dll
Gearbox don't remember

.dll
Now you just have to select your amp, your effects, and you're ready to have fun, just record, remember that by selecting the "software" button, you can tweak the Gain knob in that section so you have all balanced.
What I'm not quite sure, is, if you are able to record a DRY guitar (no effects, no amps, nothing) and then select the Plugin (VST) for mixing/editing the track(s).If someone could help me out on that question, I'd really appreciate it, for instance, on Reaper you can record a Dry guitar, then press the "FX" button, select your plugin and add whatever you want (post mixing/post mastering), I'm not sure, or I couldn't find a way to do the same with Riffworks, I only can use the Plugin as a Pre (no dry instruments, for modifying it later)
Riffworks and Gearbox get along very well, I've got the Gold Bundle and it's a non-stop options to choose from, Silver is still good, has great amps as well, it only depends on what kind of amps and Fx's you are looking for - that Riffworks does not have but are really good! - (For instance, reverse delay and the Synths are quite amusing for doing strange noises)
Have fun, if you have further questions, people here are happy to answer.
Cheers,
Paul